Some of the bororas species school nicely, I like Bororas Brigittae. Also Ember Tetra, really nice colouration, I can't say for sure that they school but I would have thought so.
Celestial Pearl Danios are IMO the best small unusual looking fish. With their slightly bent body and spangled spots, i love them.
Harlequin Rasboras are also nice, as mentioned though they can be a little pricey also but schoal well and in planted tanks the coppery hues really accentuate a scape.
Its a 10 Gal betta tank. I have 4 pygmy corys and I am waiting for 2 more. I got 6 Neon tetras today I have always wanted them but never got them because they would be food for my cichlids. They are also Dirt cheap $1 per fish I wanted the Galaxy Danios but they are $5 per fish. SO I went with the Neons for now. Thanks guys.