It's not a 'simple' way, but I use viemu in Visual STudio, where you can search for things in the vi way: you position your cursor on a word, press * and it will search for the next occurrence of that word, and highlight all matches. # does the same but backwards. So viemu gives you highlighting of search terms, in Visual Studio from 2003 onwards.

It also has vi-style regex searches, and it also highlights matches in that search mode.

In vim, it's :set hlsearch http://vim.wikia.com/wiki/Highlight_all_search_pattern_match...

Emacs has many ways of highlighting search terms: http://stackoverflow.com/questions/385661/emacs-highlight-al...

Have you looked at ReSharper? It does usage highlighting (http://www.jetbrains.com/resharper/features/navigation_searc...) The extra functionality it adds to VS 2008 & 2010 is really useful. I started using it about a month ago and kicking myself I didn't invest in it ealier.