The Blister [WS] series of gadgets, Blister [CPU], Blister [RAM], and Blister [HDD] are some of the first and still best gadgets available for Windows Sidebar.
Multiple windows from multiple applications on a typical multitasker's desktop can easily get out of hand. Window's Explorer has a tak bar suited for a few applications, but even reduced to icons they can still become too many to handle.
Pocket TV Browser is a popular tv-listings application from DoubleBit Software that uses XMLTV formatted xml. Unfortunately it is no longer supported, and changes to the xml schema have hidden bits of information from users. TVTweak rearranges the data so that all the information in the listings xml is exposed to users of Pocket TV Browser.