Searching with previews like Quick Look!
This application might not be as relevant when Mac OS Leopard comes along, but for now, it is great! It is called "SpotInside" and it lets you quickly search for words that might be inside the document you are looking for. What is great about it: it is super fast, much faster than Spotlight and as soon as you click on one of the search result, a preview of that document or pdf appears instantly! Some of the things that need improvement: the results don't start poping up immediately when you start typing so you have to press "Enter" after entering what you want to search, and it doesn't run in the background to make it easily accessible with a quick key. You can partially solve the "no quick key" issue if you use QuickSilver. Hit "Ctrl-Spacebar" to bring up QuickSilver and enter "Spotin" to load it! You can download SpotInside here on MacUpdate.