Placefav is a social-bookmarking service for places. It was pitched to me as a cross between the Muxtape and Delicious. A better thing to compare it to is the list-making feature on reviews service Yelp.
The ultimate aim is to pass your list along to someone else as a self-contained city guide. Things like this are useful when somebody asks you for a list of places or things to do if they're visiting your hometown, or a vacation spot you might have a little extra local knowledge of. The site also offers the option to favorite other users and explore the lists of people nearby.
Like Muxtape, Placefav limits you to just a dozen spots for your favorite places. You can customize the colors, and if you've put in the addresses there are quick links for pop-out Google Maps. If you don't know the address it will do its best to guess the address of a place based on the name and city it's in. The entire list is self contained with its own vanity URL and can be accessed fairly quickly on mobile phones. Creator Kyle Bragger tells me he's hoping to build an iPhone application that makes use of the device's GPS to make entry and browsing a little faster.
Coming in later versions will be the option to make even larger lists and simply e-mail your places and have the service add it to a new or existing list. Bragger also hopes to include SMS support once he's got the e-mail squared away. You can check out the list I made by clicking the screenshot below.