Here is the status of the current vB3 importers:

http://www.vbulletin.com/forum/showthread.php?t=10 2412

Here is the Online Manual:
http://www.vbulletin.com/docs/html/impex

And the Importing How-To Thread:
http://www.vbulletin.com/forum/showthread.php?t=11 6398

Quick List
IPB (2)
phpBB (2.0.8 - 2.0.10)
Infopop eve (4.00 - 4.02)
IPB (1.1 - 1.3)
wBB (2)
Ubb_classic (6.3 - 6.7)
Open Topic & Ubb.x
DCFm (DCForum+ MySQL backend)
YaBB SE (1.5.5)
Ubb_threads (6.4)
vBulletin 3 (3.0.x -> vB 3.0.3)
Snitz (3.4.x MySQL)
Ikonboard MySQL
XMB (1.9)
CuteCast (2.0)
vBulletin (2)
ThwBoard (3)
SMF (1.0)
DiscusWare (file based)(4.00.x)
vB (1.0 RC 1)
YaBB - Gold (1.3.1)
openBB 1.0.7)
deluxeportal (2.0)
Digiposts (2.0)
Phorum (3)
Fusetalk
WebWiz (7.9)

beta :
Maxportalweb.
Jiveforums.
Xoops - Newbb
Siteframe (users & categories)
PNphpBB2 (Post nuke)
TruBB

And here is a Poll about asking customers to choose which systems they would like to have importers for:

http://www.vbulletin.com/forum/showthread.php?t=10 0464