Creating Custom Site Template Definitions in MOSS07

GLOBAL#0 = Global template (1033)
STS#0 = Team Site (1033)
STS#1 = Blank Site (1033)
STS#2 = Document Workspace (1033)
MPS#0 = Basic Meeting Workspace (1033)
MPS#1 = Blank Meeting Workspace (1033)
MPS#2 = Decision Meeting Workspace (1033)
MPS#3 = Social Meeting Workspace (1033)
MPS#4 = Multipage Meeting Workspace (1033)
CENTRALADMIN#0 = Central Admin Site (1033)
WIKI#0 = Wiki Site (1033)
BLOG#0 = Blog (1033)
BDR#0 = Document Center (1033)
OFFILE#0 = Records Center (1033)
OFFILE#1 = Records Center (1033)
OSRV#0 = Shared Services Administration Site (1033)
SPS#0 = SharePoint Portal Server Site (1033)
SPSPERS#0 = SharePoint Portal Server Personal Space (1033)
SPSMSITE#0 = Personalization Site (1033)
SPSTOC#0 = Contents area Template (1033)
SPSTOPIC#0 = Topic area template (1033)
SPSNEWS#0 = News Site (1033)
CMSPUBLISHING#0 = Publishing Site (1033)
BLANKINTERNET#0 = Publishing Site (1033)
BLANKINTERNET#1 = Press Releases Site (1033)
BLANKINTERNET#2 = Publishing Site with Workflow (1033)
SPSNHOME#0 = News Site (1033)
SPSSITES#0 = Site Directory (1033)
SPSCOMMU#0 = Community area template (1033)
SPSREPORTCENTER#0 = Report Center (1033)
SPSPORTAL#0 = Collaboration Portal (1033)
SRCHCEN#0 = Search Center with Tabs (1033)
PROFILES#0 = Profiles (1033)
BLANKINTERNETCONTAINER#0 = Publishing Portal (1033)
SPSMSITEHOST#0 = My Site Host (1033)
SRCHCENTERLITE#0 = Search Center (1033)
SRCHCENTERLITE#1 = Search Center (1033)
SPSBWEB#0 = SharePoint Portal Server BucketWeb Template (1033)

  and it looks like you have to go through this to get a new one in there.

One screw-up though: If you do all this to create a custom Document Workspace site, it'll work when you use Create Site to create it but NOT if you use the  'Send To > Create Document Workspace.' So far, the only way to address this is to edit the default definition which could get overridden with upgrades and such.