And lets try to take some user-input :
An equivalent script for searching on wikipedia is :
Search Burad's Blog
Or for wikipedia
Some more bookmarklets :
You can view source for each bookmarklet by viewing page source .
You can find more bookmarklets at : http://www.squarefree.com/bookmarklets/
See this helpful screencast on bookmarklets.
Some More Example at Wisdombay
Updated : For changing documenet backgrounds :
Change to Red
Change to green
Change to blue
This may not work with pages using css