» sharepoint.microsoft.com
Official Microsoft Site

» blogs.msdn.com/sharepoint
Microsoft SharePoint Team Blog - useful tips here

» social.technet.microsoft.com/Forums/en-US/category/sharepoint2010
Microsoft forums for SharePoint 2010

» codeplex.com
CodePlex - Various useful SharePoint community projects, including
- Community Kit for SharePoint (CKS)
- Accessibility Kit for SharePoint (AKS)

» governance.codeplex.com
SharePoint Governance and Manageability - various useful resources to help with this

» www.linkedin.com/groups?gid=58750
SharePoint users group on LinkedIn - lots of useful discussions here

» www.hostedsharepointproviders.com
Review of a number of hosted solutions for SharePoint 2010

» social.technet.microsoft.com
Old Microsoft technet forums - useful for wss and SharePoint 2007

» http://www.sharepointedutech.com
Handy list of SharePoint 2010 patches and updates giving build numbers