I use boost::icl quite a lot for text post-processing. Saved me quite a lot of time because otherwise I'd have to implement text-splitting myself...
BOOST_FOREACH is everywhere in my code :)
boost::function and boost::bind are an absolute must. Although now they are std::function and std::bind. These really help reduce the amount of unnecessary code and are just generally good for my designs (or my delusions).
I've recently started using boost::interprocess::message_queue and this is a great tool too.
I'd use a lot more, but Qt has native ways of doing a lot of things Boost does. If I ever have to program pure C++, I guess I'd become a boost::junkie :)
