From http://dotnetjunkies.com/WebLog/josephcooney/archive/2004/07/26/20312.aspx:
WSE MSDN Home: http://msdn.microsoft.com/webservices/building/wse/default.aspx
WS-* specs. on MSDN: http://msdn.microsoft.com/webservices/understanding/specs/default.aspx
Useful WSE Articles:
http://www.msdn.microsoft.com/msdnmag/issues/04/08/XMLFiles/default.aspx (Aaron Skonnard on new WSE2 features)
http://msdn.microsoft.com/webservices/building/wse/default.aspx?pull=/library/en-us/dnwebsrv/html/wsroutetowsadd.asp (Skonnard again on WS-Addressing)
http://msdn.microsoft.com/webservices/building/wse/default.aspx?pull=/library/en-us/dnwse/html/wsemessaging.asp (Simon Horrell from Developmentor on WSE Messaging)
http://msdn.microsoft.com/msdnmag/issues/04/03/XMLFiles/default.aspx (Policy - Aaron Skonnard again)
http://msdn.microsoft.com/webservices/building/wse/default.aspx?pull=/library/en-us/dnwse/html/programwse2.asp (Matt Powell takes Rock-Paper-Scissors into the realm of secure, collaborative, corporate enterprise messaging technology)
Useful WSE Blogs:
http://www.interopwarriors.com/ (inter-op)
http://pluralsight.com/blogs/aaron/ (Aaron Skonnard - known to have some insights regarding XML from time to time)
http://benjaminm.net/ (ex-patriot Aussie, UK regional drector WSE wonk Benjamin Mitchell)
http://bristowe.com/blog/ (XML Plumber, Canadian regional director, MVP)
http://weblogs.asp.net/yreynhout/
http://blogs.msdn.com/Mpowell/ (MSDN content guy)
http://blogs.msdn.com/rdias (WSE PM)
http://hyperthink.net/blog/default.aspx
http://www.dotnetjunkies.com/weblog/softwaremaker/
Transports: (sending messages via other means)
http://www.codeproject.com/useritems/SoapMSMQ.asp (Roman Kiss' MSMQ transport for WSE)
http://weblogs.asp.net/kevinha/ (Kevin has transports for MSMQ and MQSerise altho I have not seen him post a link where to get the bits)
http://hyperthink.net/blog/CommentView,guid,d337a6f5-a0c8-45b8-920e-132391eedc31.aspx (SMTP transport from Steve Maine)
http://www.dynamic-cast.com/mt-archives/000056.html (UDP transport)
Other Projects:
Plumbwork Orange http://workspaces.gotdotnet.com/plumbwork (more WS-* specs implemented using WSE 2 pipeline and idioms)
OpenNetCF http://www.opennetcf.org/CategoryView.aspx?category=Home (Casey Chesnut has implemented parts of WSE 2 for .NET CF)
Update: WSE 2 sp1 is available from here http://www.microsoft.com/downloads/details.aspx?familyid=fc5f06c5-821f-41d3-a4fe-6c7b56423841&displaylang=en
Update 2: Simon Guest's interop-centric weblog http://weblogs.asp.net/smguest/ has some interesting WSE items, including a link to this article on how the WS-* specifications evolve via workshops http://msdn.microsoft.com/webservices/community/workshops/default.aspx?pull=/library/en-us/dnwebsrv/html/wkshopprocess.asp