The Microsoft Dynamics AX support team has started a new blog dedicated to highlighting the top resources for troubleshooting issues with AX 2009. Aside from listing the issues and resources, they are hoping to engage the community via comments on the posts. Now that MSDN and TechNet are starting to catch up on useful information about the product, it's nice to see some dedicated resources to troubleshooting.
You can find the blog on the Dynamics Community site.
Aside from this blog dedicated to troubleshooting, there is another blog from the support team that I've found very useful to subscribe to. Check out the "regular" blog of the AX Support team.
And of course, never forget the official Microsoft Dynamics AX forums.