I agree with the blue betta, assuming it would get along with your other fish. I'm not so sure about the gourami... Blue guppies are good too.
PetSmart (at least in Davenport, IA) had blue rams for $2.99 each. They actually looked wonderful! Bright colors, fins spread open, hungry. I couldn't resist.I don't think they are the easiest of fish to keep though. And I think they may be a little picky about pH and a little intimidated by other tankmates.
I second the electric blue rams if you can pay that much. They are awesome fish.
If you don't mind a little yellow/orange with your blue, what about Bosemani rainbows?