Kyrii Vore 2 (split version) original by Hana Keijou (Character by G-cat)
The original artwork can be found here.

Additional Edit Rules: Use Rectangular Part. (Rule Descriptions).
After Edit Rule: Add Text ("by Hana Keijou"). (Rule Descriptions).
Credit Rule for Hana Keijou: Required. (You have to credit the author somewhere in the game.)
Credit Rule for G-cat: Optional. (Credit the author somewhere if you want to.)
Download

Junglerush (cut version) orginal by RedWerewulf
The original artwork can be found here.

Additional Edit Rules: Full Edit Rights.
Credit Rule: Required. (You have to credit the author somewhere in the game.)
Download

Internal Throat Shot by RaggedRook

Additional Edit Rules: Use Rectangular Part. (Rule Descriptions).
Custom Edit Rule: "If the user has to use, say, seamless tiling, or smudge the edges to make it tile correctly, I'll allow that also."
Credit Rule: Required. (You have to credit the author somewhere in the game.)
Download

Untitled by Zinou

Additional Edit Rules: Use Rectangular Part. (Rule Descriptions).
Credit Rule: Optional. (Credit the author somewhere if you want to.)
Download

Eskoz's Artwork Collection by eskoz

Additional Edit Rules: Full Edit Rights.
Credit Rule: Required. (You have to credit the author somewhere in the game.)
Download

Stomach BG by Blazbaros

Additional Edit Rules: Unknown.
Credit Rule: Required. (You have to credit the author somewhere in the game.)
Download

NOTE: Keep in mind that some authors did some of their works in cooperation with other people. If so, you have to gain the permission from all cooperated authors as well to use the particular resource.

Hana Keijou's Gallery
Additional Edit Rules: Use Rectangular Part. (Rule Descriptions).
After Edit Rule: Add Text ("by Hana Keijou"). (Rule Descriptions).
Credit Rule: Required. (You have to credit the author somewhere in the game.)

RedWerewulf's Gallery
Additional Edit Rules: Full Edit Rights.
Credit Rule: Required. (You have to credit the author somewhere in the game.)

Dantha's Gallery
Additional Edit Rules: Full Edit Rights.
Credit Rule: Required. (You have to credit the author somewhere in the game.)

Thor66's Gallery
Additional Edit Rules: Edit Text Elements. (Rule Descriptions).
After Edit Rule: Add Text ("by Thor66"). (Rule Descriptions).
Credit Rule: Required. (You have to credit the author somewhere in the game.)

E-akahele's Gallery
Additional Edit Rules: Edit Text Elements + Graphical Parts, Use Rectangular Part, Apply Filters. (Rule Descriptions).
After Edit Rule: Add Text ("by E-akahele"). (Rule Descriptions).
Credit Rule: Required. (You have to credit the author somewhere in the game.)

ChaosEmerald2's Gallery
Additional Edit Rules: Full Edit Rights.
After Edit Rule: Add Text ("by ChaosEmerald2"). (Rule Descriptions).
Custom Rule: Only images of the category "Felarya-Sprited" in his gallery can be used.
Custom Rule: "I would like to be notified that my work is being used in a game or other form of media, and have a link provided to me so that I can see how it is being used. If I disapprove of the use, the person must remove the work and find an alternative."
Credit Rule: Required. (You have to credit the author somewhere in the game.)

Deathworks' Material Gallery at Photobucket
Additional Edit Rules: Full Edit Rights.
Credit Rule: Required.
Note that this is only the material gallery and its subgalleries. The rest of my gallery at Photobucket are not included.

Simple Throat Tileset (RPG Maker XP) by gtsfan9 & Karbo
I made that Tileset by cutting, stretching, skewing things out of one of Karbo's drawings. It's pretty simple and contains only 2x3 parts.

Additional Edit Rules: Use Rectangular Part, Apply Filters. (Rule Descriptions).
Credit Rule for Karbo: Required. (You have to credit the author somewhere in the game.)
Credit Rule for gtsfan9: Optional. (Credit the author somewhere if you want to.)
Download

Game Sound Package (69 Sounds) by several authors
Some sounds I collected from http://freesound.org/. I cut some of them to remove background noises and to split them up.

Additional Edit Rules: Full Edit Rights.
Credit Rule: Required. (You have to credit the author somewhere in the game.)
Download (Mirror)

RPG Maker XP Sample Project by gtsfan9
Contains some of this resources to demonstrate the use of them.
(The game is fully playable, however keep in mind it's a demo project not a real game.)
Additional Edit Rules: Full Edit Rights.
Credit Rule: Optional. (Credit the author somewhere if you want to.)
Download (Mirror)

CallEvent Script (RPG Maker XP) by gtsfan9
Simple script to call an event from another event.
For example: If you have five events which should all do the same thing you can, instead of copying them, use one as "base-event" (or add a new event to be used as base-event) and make, using this script, all other events call that base-event. This reduces redundancy.
Additional Edit Rules: Full Edit Rights.
Credit Rule: Optional. (Credit the author somewhere if you want to.)
Download

Tileset Tools (RPG Maker XP) by gtsfan9
Tools to create and modify tilesets.
Actually containing: Tileset Generator 1.0, Tileset Builder 1.0.2, Tileset Enlarger 1.0.
Note: You may need the .NET Framework 2.0 Redistributable Package to execute them.

Credit Rule: Optional. (Credit the author somewhere if you want to.)
Download

Other RPG Makers
There are other RPG Makers in the world out there. You can either get OHRRPGCE, or one of the alternatives listed on their alternatives page. In short, if you want to be cross-platform, you'll want to check into one of these, as RPG Maker XP RTP does NOT work in WINE for Linux. If the aforementioned links do not work, then try to google for these RPG Makers:

* Verge
* Ika
* Sphere

http://www.freesound.org/
http://www.stonewashed.net/sfx.html
http://www.vgmusic.com/

General notes for image editing:

• If an image contains multiple images (comics for example) then all rules defined for that image appear for any single part (sub-image) of the base-image. The user may generally be allowed to cut and use only the sub-images from that base-image (this doesn't mean that rectangular cut rights appear to the sub-images).
• All edit rules appear for statical editings only. However a game can also apply filters, move images above others, cut off parts of images etc. which is generally allowed but has to be animated and not statically applied (all the time) except the corresponding edit rule is given.

Edit Rule: Sizing and Rotating (Default)

Means sizing and rotating of the whole image.
Note: This is a default rule. All resources provided allow this rule by default.

Edit Rule: Joining (Default)

Means joining of different images together. They must be joined at their borders which must be obviously different. They may not flow/proceed from one to another. (Means you can't for example cut off a head from a character and join it with another characters neck.)
Note: This is a default rule. All resources provided allow this rule by default.

Additional Edit Rule: Edit Text Elements

Means adding, removing and modifing of text elements (but not their graphical parts like backgrounds etc).
This rule allows you for example to refill texts in speech balloons.

Additional Edit Rule: Edit Text Elements + Graphical Parts

Means adding, removing and modifing of text elements and their attached graphical parts (like speech balloons, lines pointing from a text to the image etc.).

Additional Edit Rule: Use Rectangular Part

Means cut out a rectangular region from the image and use this part instead of the whole image.
This rule allows you for example to use only a face of a character.

Additional Edit Rule: Apply Filters

Means applying filters like sharping, blurring, recoloring etc. the image should be still recognizable.

Additional Edit Rule: Full Edit Rights

Means any way of editing the resource without any restrictions.

After Edit Rule: Add Text ("the text which has to be added")

Forces you to add a specified text like "by <authorname>" in one of the image corners after the image was edited and the original sign of the author has been removed. It must be in Arial, 8pt, well readable color and fully visible.
Note: This rule does not require any "Edit Text Element" permissions.