On the TechNet you can find numerous articles that can be related to BizTalk Administration:
Another good resource for BizTalk Administrators is of course MSDN, where you can find a lot of information:
There are a few white papers on BizTalk administration:
At the BizTalk Server Developer Center you can also find resources for BizTalk administrators. Although the title can be a little misleading as it may look like developer focused. However you will find resources and information that is more administrator specific:
There are two courses you can take that are targeted towards BizTalk Administrators:
There is one virtual lab on BizTalk Administration:
On LinkedIn you can find groups targeted for BizTalk Administrators:
These articles is also available in the following languages
Added the category Virtual Labs