Google-Seems cliche, but this belongs here anyways. This is the ultimate resource site. You can find any game, character set, monster graphic, song, etc... on this site.

Gamefaqs-This site has information and message boards on virtually every site in existence. Including RPG Maker.

Gaming World-This is a huge RPG Maker site with forums, tutorials, resources, and even games!

Blade2k-Another RPG Maker site, basically the same kind of stuff as Gaming World. Also, my forums are combining with this site very soon.

Ultima Island-Another awesome RPG Maker site with forums, games, and resources. I highly reccomend you check this site out.

Charas-The ultimate resource site! Not only does this have a huge database of resources, but you can also create your own!

Vgmusic-This site has lots of midis for your RPG. Very useful.