SQL Server SP2 can be downloaded here.  Not too bad at about 280MB to in size.  
http://www.microsoft.com/technet/prodtechnol/sql/2005/downloads/ servicepacks/sp2.mspx

So what's new in this SP2, well as has been typical of MS lately, they are releasing new features, so make sure you know what you are getting along with the fixes.
http://download.microsoft.com/download/2/B/5/2B5E5D37-9B17-423D-BC8F-B11ECD4195B4/WhatsNewSQL2005SP2.htm

So what's been fixed in this SP2.  Now this is the important stuff...what has been fixed. 
http://support.microsoft.com/?kbid=921896

SQL Server 2005 BOL Update (Feb 19, 2007).  To coincide with the update, the BOL team didn't want to be left out so they also had the Book Online updated.  They have been doing a good job lately getting new materials into BOL!  
http://www.microsoft.com/technet/prodtechnol/sql/2005/downloads/books.mspx

Finally, the SQL Server 2005 Best Practices Analyzer (FEB 2007 CTP) was released.  Make to to check it out and see how you stack up.
http://www.microsoft.com/downloads/details.aspx?FamilyId=DA0531E4-E94C-4991-82FA-F0E3FBD05E63&displaylang=en