LinkyNo Gravity started out as a homebrew PSP game. A small-ish demo was released, and with a little searching you can still find it (only if you have an original model PSP with CFW. Doesn't seem to work on Slims). The demo must have impressed some people, so its being turned into a full PSN title for PSP. Hooray!
No Gravity is a space shooter, reminds me very much of Colony Wars. Watch the trailer and be impressed.