The categories have been condensed and some forums are currently listed to be retired (if they are very underused). Some of the forums on the retired list may be a surprise BUT it's important to remember that the list has yet to be finalized, and we may ultimately combine some of the lesser-used forums together.
These forums from Computers & Internet are currently in the retired list:
Bloggers
Apple Users
Open Source and Free Software
Website, DB, & Software Developers
(Apple Users probably shouldn't be there, it gets a reasonable amount of traffic.)
You can now find Computer Help & Support on the Help & Search page, where it is listed as General Computer Help (although if you click through to the forum, the old name is there -- these are things that will be worked out prior to the full launch of DU4, remember we're just testing at the moment).
Finally, if you subscribe to any forum (click the Subscribe button at the top of the forum) then the forum will be listed in your left-column navigation, so you can build your own list of navigation links there.