Alan has a good point – location really narrows or expands your choices.
I have heard the best things about the Quicklearn Deep Dive classes (for
more experienced developers with Biztalk experience) and Developmentor
(www.develop.com) classes.
Developmentor has two classes for 2006 and I think a few for 2004. I
think they are more beginner level but the Guerrilla class is intense.
Oh, http://www.biztalk-training.com also offers some good classes – they are
self paced, CD based and I think it’s just for 2004.
I would focus on training on 2006 since most of the topics are relevant to
2004 as well.
Hope this helps.