www.nikoli.co.jp/en - The main company that invented and popularized most of the Japanese logic puzzles seen today
www.nikoli.com/en - A website that has many different Japanese logic puzzles to play online
www.brainbashers.com/games.asp#logic - A website that features many different Japanese logic puzzles with new puzzles daily
www.chiark.greenend.org.uk/~sgtatham/puzzles - A website with many programs to play different puzzles; it generated most of the puzzles on my site
www.puzzles.com - A website that has many different puzzles to play
www.janko.at - A website with many different puzzles and the java applets I use for many of my puzzles (unfortunately it is in German; English translation here)
www.wiki.logic-masters.de/index.php?title=Meta:Mainpage/en - This page is a collection of other logical puzzles and how to play them
www.menneske.no/eng - A site that features many different generated puzzles
www.puzzlebeast.com - A website with many unique puzzle types and some sliding block puzzles
www.stetson.edu/~efriedma/puzzle.html - A website that features many great, original puzzles
www.clickmazes.com - A website with many logic-oriented unique mazes
www.logicmazes.com - Another site with many logic mazes (as the title suggests)
sudoku games - A fast growing UK games community with trivia, puzzles and brain games constantly added and updated. You can play individually for brain training fun or compete against other real people in multiplayer cash jackpot games.