As someone else pointed out in another thread, there are tons of mobile games available free for OTA download at this site:
Mobile 9
That said, most of the games I've tried on there don't work on the Pearl. Two that do, however:
Age 0f Empires 3 (Runs OK, but flickers some.)
Nuts (Anybody remember Indiana Jones and his Desktop Adventures? Picture Indy as a squirrel.)
If anyone knows of more of these that work, please post.