Well... you can get a partial listing by going to www.towerhobbies.com and typing servo in thier search box.

You'll find probably over 100 different servos by several manufacturers... and then there's more manufacturers which Tower doesn't carry.

A nice feature of thier site is you can get the technical specs of each product, and read up on the basic info they place in each product's description. (you don't have to buy from them to read the info... )

The 3003 and 3004 are "standard" size and power servos, with the main difference being the 3004 is ball bearing. One note... the Tower TS-53 is a relabeled Futaba S-3003. Peel the label, and the Futaba designation is molded in the case. The TS-53 is close to $9, the S-3000 is close to $14... and the only difference is a label has been stuck on the CHEAPER servo.

There's a kit available with 4 case tops that upgrades S-3003 to ball bearing, and the case tops are a stronger material than the S-3004 tops. I use this kit to replace case tops that have had the mounting lugs broken off. Appx $14 for the kit. (which combined with 4 new TS-53's is cheaper than 3 S-3004's. )