GPWindow is Everything Dynamics GP. Try the Custom GP Search engine which searches high quality GP Blogs, and the Microsoft Dynamics GP Community Forums.
My favorite link, is the page David Musgrave has been maintaining for Dynamics GP 9, GP 10, GP 2010 product downloads, service packs and System Requirements. Scroll down to the appropriate section.
veeyeskay explains the importance of keeping clients on the latest version, and the download links for GP Service Packs (GP 8 onwards) in his post Important Links for Microsoft Dynamics GP
Mark Polino maintains an Office Live document which has a lot of very useful download links to all GP related software, GP Table Reference, links to his presentations and other reference items. Victoria Yudin maintains an excellent page with GP, FRx and SQL Resources, and other links here.
In the FRx Downloads sub section, there is an excellent page by Vitoria Yudin - FRx Service Packs - with all the download information for FRx Service Packs (SP 1, SP 2, SP3, SP 4 , SP 5, SP 6 , SP 7 , SP 8 , SP 9 , SP 10, SP 11) and their version information. You can find FRx full download link at FRx 6.7 Full Download Links.
You can find the fantastic all empowering Support Debugging tool Download via the Support Debugging Tool Portal
Snapshot Tool Download - SnapShot for Microsoft Dynamics GP
Rapid Implementation Tools Can be found here - Rapidly implementing customers on Dynamics GP 2010!
Professional Services Tools Library Download