This list was originally created by the Microsoft BizTalk support team. Feel free to add to it.
Do not let suspended instances accumulate. They should be handled promptly by either being terminated or successfully resubmitted. If these items reach in the thousands, performance can be impacted. MsgBox Viewer also breaks down the suspended instances by host.
919776 Description of the SQL Server Agent jobs in BizTalk Server http://support.microsoft.com/default.aspx?scid=kb;EN-US;919776
Another important place to find a huge amount of BizTalk related articles is the TechNet Wiki itself. The best entry point is BizTalk Server Resources on the TechNet Wiki. Read suggested related topics: