The best replacement for sidebar is windows sidebar.

The best alternatives to sidebar are rated as following:
★★★★★  windows sidebar
★★★★  swapps
★★★★  glove box
★★★  sideshow
★★★  sidebar
★★★  desktop sidebar
★★★  aside
★★  google sidebar
★  widget
★  rainmeter
★  vista sidebar
★  google desktop
★  side bar
★  rainlendar

Your alternative for sidebar is not listed? Suggest!
Speaking about sidebar, one probably shouldn't forget about gadgets.

Other search terms related to sidebar and their ratings are:
★★★★★ gadgets
★★★ gadgets for windows xp
widgets
You have in mind a companion for sidebar and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of sidebar in all years. Click on graph for more.
sidebar
windows sidebar
swapps