I've been doing some work with Integration Services in the past few weeks. Some resources have proved to be a bit too much like hard work, others have been more useful.

MSDN has a series of tutorials

Blogs:
There are some good blogs kicking around - these are the ones that I've had a few hints and tips from and that have been added to my RSS aggregator:


Forums:
Webcasts:

Books:

Update: After signing up for one of the webcasts the other day, a useful email came through pointing me at MSDN Integration Services which has an impressive set of links.
Futher Update: Thanks to Linda for pointing out via Daniel Read's index that there is an index to the SSIS articles on Database Journal.