Remember this URL http://www.janko.at/. It is the personal homepage of Angela and Otto Janko. As well as documenting much of their home life such as their pets, garden and hobbies, there is also a whole treasure trove of brainteasers here and make up a great bulk of the site. Taking submissions from puzzle authors and categorising them by type, size and difficulty there is a whole wealth of fun times to be had. Better still, many of the popular japanese logic puzzles are all solvable interactively in custom designed Java applets which allow you to save progress, check for errors and retrace your steps as well as including 'what if' markers so you can graphically check for contradictions if you are into that kind of thing.
Bonus points to anyone who can find puzzles I've submitted to this site. Oh and be sure to use google translator when you get to the puzzles section as the website is written in German. There are a collection of flags at the top left hand corner of the Puzzle/Raetsel section. This site is regularly updated and continues to expand.
Oh and just for another good timewaster, try Picture Logic for some of the popular Hanije puzzles, also frequently updated.