The Monaco Sidekick 3 cradle is convenient because it will charge your SK3 and an extra battery without fumbling with cables, but it is also a little lame because that is all the Monaco dock really does. Sure it includes a USB port to transfer files to your PC, but most syncing with the SK3 is done wireless via T-Mobile's website so the USB cable isn't as useful as thought. The HipTop3 folks like the dock because it holds the SK3 vertically, therefore eliminating the horrible task for having to pick up your phone to see the IM, SMS or call. At least it is a cheap: $20.
Monaco Sidekick 3 Cradle [Hiptop3]