Bemanistyle 6.0 The first on the list probably since it can help you find basically whatever your looking for whenever you want. they have froums, music downloads and basically one of the best resources. Djparanoia is now even selling some assorted bemani merchandise. 7.0 is also being worked on now and will be brought to us in the near future.
DDRFreak is probably the best resource for any fan of Dance Dance Revolution. They have the latest updates in the world of DDR and offer machine locations all around the world. The forums are also really nice to go to and are mostly DDR related.
aaron in japan Aaron's website. Aaron, who is good friends with the greatest DDR player's in Japan or ever for that matter, has created a website where he has many interesting DDR tools. He has a score calculator and many random arcade game related images. If you thought you were something check out the videos section to see how the skills of Aaron, Take, and Yasu(as well as many other very good players).
Homeii's website. My personal favorite website. Is the ultimate drummania resource. This site is mostly about the simulators for drummania and its sim-files, but they have a lyrics database as well which contains most of the lyrics for all sorts of drummania songs. A weekly tatsujin video is also available which usually features a really impressive drummania player. A site belongng to a GDA creator(I don't know his name). His site features many songs from DES-ROW. Very well done GDA's in my opinion.
Temis's(?) tatsujin videosWebsite containing videos of the famous Drummania player Temis. Very impressive videos, on some of the hardest songs avilable. Also contains some videos from pop'n music(which are really well played). Some of his newer vidoes can also be found at homeii's site from time to time.
Chatora's CafeGuitar freaks GDA's for bandjam. they have many, many, good songs for guitar freaks just copy the guitar part and paste it into the drum GDA.