Thanks for that, one less thing I don't know. I had been googling dual bridge.
As you explore, you'll typically find two common h-bridge ICs used; these ICs, while not extremely efficient, tend to both be very inexpensive. You'll find many driver boards and shields made with them.
They are the L293 (and the SN745510 drop-in) and L298. Both are "dual h-bridge" chips; the L293 (typically D variant) / SN745510 can handle 1 amp per bridge, maximum, which is useful for many small hobby motors, while the L298 can handle 2 amps per bridge. Generally both of these chips should have a proper heatsink installed to reach the maximum current level.
A couple of other things to keep in mind on the L298: First off, it isn't designed to work on a standard 0.1" pitch breadboard or protoboard. To use it properly (bare) on these boards, you will need an adaptor PCB (I've used this guy's adaptors in the past - they are well made and inexpensive: http://www.jrhackett.net/L298adapter.shtml
Secondly - the L298 (unlike the L293/SN745510) is designed as a "bridgeable" h-bridge. See the datasheet for more information, but basically what this means is that you can hook it up in a particular fashion to use the two independent bridges as a single h-bridge, which allows you to drive a motor that can pull up to 4 amps.
Finally - the while the L293/SN745510 can't be "bridged" in the same fashion, I have heard (completely anecdotal) of people "stacking" these chips and soldering the legs together to increase the current handling. This isn't defined as permissible in the datasheet for the h-bridge, so YMMV. There is also the issue with getting heat out from the "middle" of the stack...