http://www.sloog.org/

"Sloog is a bookmarking service for Second Life residents. It allows users to save favourite places and avatars and search for them later, both in-world with a simple plug-in (HUD) or via web browser at www.sloog.org"

Browse locations in SL by tag (keyword)! Nifty! It's like del.icio.us for SL locations! And, it is currently free (as stated on their website, April 2007). You can get a HUD in-world at the Mosi-Mosi offices, Mosi Mosi (155, 86, 0).

Read more about how the whole thing works at http://www.sloog.org/about