okies. i started with 2 electric yellow cichlids cuz they really caught my eye. turns out they're one of the most popular and readily available in most pet stores, and easy to care for.
go here
http://www.cichlidrecipe.com/cichlidchart/flashchartd.html (maximize your internet window and scroll down to the bottom before the page loads so it comes up big enough to read)
the light blue squares mean compatable, the blue squares mean use caution, the dark blue squares mean don't mix/danger. the gray squares mean don't mix because they might breed and you'd end up w/ a weird hybrid if different species from the same genus are involved. the names across the top and down the side are genus, so in theory you could pick any species and they'd mix ok.
electric yellows are labidochromis, if you look across, they have the most light blue squares of any of the other genus', so you know they mix well. use that chart w/ the link i gave ya above and you could keep yourself busy for hours

good luck.
oh, and cichlids go by the same rule, 1-2 gal per adult inch, keeping in mind that you'll need to give a little more room because of their aggressive nature and all the rock decor you'll want will push some gallonage out. some of the bigger cichlid species need bigger tanks, but you should be alright w/ a community of the smaller colorful ones. just for instance, most of the labidochromis species stay around 3-5" at adult size.
as with anyone doing cichlids, just do a lot of research (and visit some pet shops to see the fish) before you decide what you want. and sorry for the long post