I work in a university setting, so I have requirements that differ from most independent photographers. I archive my raw files on a server here in my studio. All the files have complete caption and keyword information applied with Photo Mechanic. Using Spotlight in Mac OS, I can search the metadata and find whatever files I need. For ease of browsing, raw files are organized by date, so all the 2009 photos are in a 2009 folder, in subfolders by date shot (20090429 would be today), then in individual folders by subject/assignment. I understand that the latest Windows search system is comparable.
Of course, this requires that every file get at least some well thought out keywords, and a full caption is even more helpful. Lucky for us, that's easy to do using Bridge, Photo Mechanic, Lightroom, etc.
To distribute photos to my on-campus clients (art directors, news and communication staff, web team, etc.), I use a web-based archiving system from WebDAM (also called Spitfirephoto.) Probably not much use to most folks on this board, but someone out there might need it. That catalog contains processed JPEG files, ready for web or print use. The archive harvests all the caption and keyword data, which becomes searchable within the web site.
For personal/freelance use, I really like PhotoShelter. PS is another online, web-based archiving and distribution system. It's intuitive, easy to use, easy for my clients to use (important!), and not too expensive. If anyone is looking for a web-based system, this one is very good. (Usual disclaimer -- I'm just a customer.)