Dee-Ann LeBlanc: Linux at Work and Play
Ever wondered how much effort it would take you to duplicate a particular open source project? Check out ohloh, where you can feed in information about a particular project and let their software tell you how many man-hours or how many US dollars it would take to reproduce. Projects can be compared, project "stacks" can be made (for example, a LAMP stack) for cases where projects sit on top of other projects, and so on.
Someone put my husband's Maia Mailguard project on there and he was I think a bit surprised but pleased at the results.