Well, I can give you the "scoop" on a couple:
Goju-ryu has very rooted, solid stances. Shiko-dachi, no kiba-dachi. Blocks are circular instead of linear, using the concept of turning the opponent. Body strikes are off-center, targeting the heart or liver instead of the sternum. Kicks are waist high or lower. Think fighting on a narrow dock or boat, you must keep your balance and don't have much room to dodge or jump. Traditionally only 12 kata. The "wax on, wax off," and "painting the fence" moves from The Karate Kid are Goju-ryu.
Sh*to-ryu utilizes linear blocks and strikes and may allow higher kicks (some schools practice head kicks). Many kata have light, quick dodging or jumping moves, even dropping to the ground. One-legged crane stances are also in some kata. Think out in a field or a large open space, with plenty of room to dodge, jump and run. Most kata lists state 54 for this style.
Shotokan is also linear, but more rooted. Where sh*to-ryu uses nekoashi-dachi (cat stance) Shotohan uses kokutsu-dachi (back stance). The chamber (set up) for knifehand blocks is different from sh*to-ryu. It's hard to describe the differences, so I'll show you the same kata done by the different styles.
Here is a comparison of the same kata:
sh*to-Ryu Pinan Shodan:
http://www.youtube.com/watch?v=AnQ7uc_H7tcGoju-ryu Heian Nidan: (Funagoshi renamed many kata from Okinawan to Japanese)
http://www.youtube.com/watch?v=6Hc1NMdjU9UGoju-ryu doesn't do Pinan/Heian kata, so here's a beginning kata from Goju-ryu:(notice the circular blocks)
http://www.youtube.com/watch?v=iqg35Gr6gxcThe style I study, Shudokan, is somewhat eclectic, so we do some straight-line and some circular movements. We parctice all 12 Goju-ryu kata at black belt, but most of our kata come from sh*to-ryu.