Although it isn't the biggest site with the most amount of fish, it's got the most common stuff and is nicely laid out with decent amounts of info on each fish.
http://www.thetropicaltank.co.uk/Fishindx/fishindx.htm
Look at things like Tetras, Corys, Barbs, Rasboras, Loaches, Gouramies, all the livebearers.
That should give you a good idea.
And if you want different fish or more colourful looking fish, look at malawi and tanganyika cichlids, they're under the cichlid page.
A nice tank set up with a lot of rock in it and some african cichlids can look very nice.
If you're looking for fish that will be more of a pet and have more of a personality etc, then looking at the American cichlids.
I hope this will give you some sort of idea on the sort of fish avaliable.
As for buying them online, there isn't many sites in the UK that do that.
http://www.tropicalfish4u.co.uk/ is one of them.
http://www.thetropicaltank.co.uk/Fishindx/fishindx.htm
Look at things like Tetras, Corys, Barbs, Rasboras, Loaches, Gouramies, all the livebearers.
That should give you a good idea.
And if you want different fish or more colourful looking fish, look at malawi and tanganyika cichlids, they're under the cichlid page.
A nice tank set up with a lot of rock in it and some african cichlids can look very nice.
If you're looking for fish that will be more of a pet and have more of a personality etc, then looking at the American cichlids.
I hope this will give you some sort of idea on the sort of fish avaliable.
As for buying them online, there isn't many sites in the UK that do that.
http://www.tropicalfish4u.co.uk/ is one of them.