You can Play Hacked Pokemon rom hacks Online for Free here
http://www.vizzed.com/vizzedboard/retro/index.php?category=10&search=pokemon
Here's a list of Hacked Pokemon game hacks:
SMB2 Pokemon Hack rom, Pokemon of the Past rom, Pokemon Diamond rom, Pokemon 4-in-1 rom, Pokemon Legends rom, Pokemon Master V2.0 rom, Pokemon Z2 (silver hack) rom, Pokemon Yellow Upgrade rom, Pokemon Yellow (hack V1.2) rom, Pokemon Topaz (silver hack) rom, Pokemon Tanero (yellow hack) rom, Pokemon Silver Advance Adventure rom, Pokemon Obscure (gold hack) rom, Pokemon Mystic (silver hack) rom, Pokemon Latios (silver hack) rom, Pokemon Dreamland (gold hack) rom, Pokemon Cute (yellow hack) rom, Pikamon Silver (pokemon hack) rom, Oak Vs Gio (pokemon yellow hack) rom, Bokemob (pokemon blue hack) rom, Cokemon (pokemon blue hack) rom, Meowths Adventure (pokemon hack) rom, Oak\'s Dream 2 (pokemon red hack) rom, Oak\'s Dream (pokemon blue hack) rom, Pikamon (pokemon red hack) rom, Pokemon 151 (red hack) rom, Pokemon - Johto Journeys (hack) rom, Pokemon - Next Generation (hack) rom, Pokemon Amsterdam (red hack) rom, Pokemon Aqua (red hack) rom, Pokemon Black Special Palace Ed. rom, Pokemon Blue Before Elite rom, Pokemon Blue (enhanced) rom, Pokemon Blue Upgrade rom, Pokemon Breeders Edition (blue) rom, Pokemon Brown (red hack) rom, Pokemon Generations (red hack) rom, Pokemon Girl (red hack) rom, Pokemon II (red hack) rom, Pokemon Meowth (blue hack) rom, Pokemon Meowth (red hack) rom, Pokemon Neo - Adventure (red) rom, Pokemon Neo - Rocket (blue) rom, Pokemon Pink (red hack) rom, Pokemon Revolution (red hack) rom, Pokemon Rocket - James (blue) rom, Pokemon Rocket - Jessie (red) rom, Pokemon Z (red hack) rom, Pokemon Rosa (red hack) rom, Pokemon Brown 2009 (red hack) rom, Pokemon Land (hack) rom, Pokemon TRE-Team Rocket Edition rom, Pokemon Rusty Gold (hack) rom, Pokemon Prism (gold hack) rom, Pokemon Pikachu Edition (crystal hack) rom, Pokemon Crystal World (hack) rom, Pokemon Crystal Redesign (hack) rom, Pokemon Crystal All (hack) rom, Pokemon Blue Sea Edition rom, Pokemon Chaos Black rom, Pokemon Dark Cry rom, Pokemon Elements rom, Pokemon Frosty rom, Pokemon Kohaku Adventures rom, Pokemon Legends rom, Pokemon Liquid Crytal rom, Pokemon Liquid Ocean rom, Pokemon Obsidian rom, Pokemon Orange rom, Pokemon Orchid rom, Pokemon Quartz rom, Pokemon Rebirth rom, Pokemon Rijon Adventures rom, Pokemon Shiny Gold rom, Pokemon Soft Red rom, Pokemon Tiberium rom, As Aventuras de Pikachu (pokemon hack of zelda) rom, Mew2's Super Mario World (pokemon) rom, Pokemon, Mewtwo Strikes Back rom
Some of my Favorites:
Play Pokemon of the Past Rom Hack
http://www.vizzed.com/vizzedboard/retro/game.php?id=1040
Play Pokemon Silver Advance Adventure Rom Hack
http://www.vizzed.com/vizzedboard/retro/game.php?id=4772
Play Pokemon Rusty Gold (hack) Rom Hack
http://www.vizzed.com/vizzedboard/retro/game.php?id=5073
Play Pokemon Crystal Redesign (hack) Rom Hack
http://www.vizzed.com/vizzedboard/retro/game.php?id=5077
Play Pokemon Liquid Crytal Rom Hack
http://www.vizzed.com/vizzedboard/retro/game.php?id=11276
Play Pokemon Dark Cry Rom Hack
http://www.vizzed.com/vizzedboard/retro/game.php?id=11271
Play Pokemon Frosty Rom Hack
http://www.vizzed.com/vizzedboard/retro/game.php?id=11273
Play Pokemon Chaos Black Rom Hack
http://www.vizzed.com/vizzedboard/retro/game.php?id=11270