Sanus is one of the world's leading manufacturers of under cabinet TV mounts.
While Coby, GPX and Memorex make actual TV units that install under the cabinet (entire units that include the tuner and possibly a DVD player), Sanus focuses more on mounts which can be used to attach an LCD TV.
LCD units are generally light-weight, which makes them possible to mount under a counter or cabinet. Rather than having to mount to the wall, and finding a stud, these mounts by Sanus can attach directly to the under-side of a cabinet, and the weight of the LCD can be fully supported.
Sanus also makes TV mounts which attach to the wall instead of under the cabinet. These are generally for larger units, and require being mounted into a stud.
Most of the mounts made by Sanus are moveable; in other words they swivel, allowing the TV to be adjusted for the perfect viewing angle. This can be a problem in situations where the TV will be moving, such as in an RV or a Boat. Look for mounts that have locking devices, or you may have to rig something to keep them stationary, such as securing the mounts to the desired position with wire.
Based on consumer reviews from sites such as Nextag and Amazon, Sanus TV Mounts receive the highest rating among LCD TV mount suppliers.
Christy - Under Counter TV info from http://undercountertv.net