Not much, really. They're both very good DDL forums, and if you're into using DDL then they should both be in your bookmarks.
I think part of the confusion over Bolt.org is that until recently it was known as Rapid.org. Because rapidshare was suing sites for infringement of it's name, and with their recent changes which weren't very popular with uploaders, they decided to allow other filesharing hosts rather than being exclusively rapidshare, and so, they decided to change their name.
Still seems to be mostly rapidshare links. Some forums almost completely switched over months ago.
Bookmarks