You could fit about 20 smaller fish (small tetras, guppies, danios etc) but depending on the individual fish you may be able to fish more or less. In your signiture you say angel fish are cool, well you could fit a couple in that tank(actually what dimensions is it?) You could fit around 10 tiger barbs or sword tails. Or you could fit some smaller cichlids in there.
Theres lots of options but like twisted penguin said we really need more info before we can help you any great deal. Mainly the tank dimensions and what type of fish you interested in.