Art

Tsunami Channel Script Site   -  I'm still figuring out what this is exactly, but someone pointed out that they have a simple way you can make little date-sim character graphics.  They would be great for testing your game engines!

~Uguu~   -  Here's a link to part of this Kanon fansite that has lots of CGs you could use for testing purposes and examples of ren'ai art.  (Note:  no hentai content :-)  )

Music and Sound FX

MP3 and MIDI Composers' Exchange   -  Maybe you can find a composer for your game here...  =;-)

Partners In Rhyme   -  This site has some public domain (not verified) MIDI files and sound effects.

Programming

The official Allegro website   -  Allegro is a great free game programming library for multiple platforms.

Allegro.cc    -  This useful site has links to free programming utilities (especially for Allegro), free games, and a forum where you can ask game-making and programming questions!    

The Dev-C++ Resource Site    -  Here you can download all the free (and legal!) software you need to get started with C++.
              
Watson's Hot Programming Pages   -  A site I recently found that can help you get started in programming.