Comparing Dropbox and Jungledisk's pricing:
Dropbox is $9.99/month for 50GB of storage. Jungledisk is $(3 + 6.75)/month for 50GB of storage.
Jungledisk seems a little cheaper at the 100GB level, assuming you're using the Rackspace cloud instead of S3.
Has anyone had any experience with the Rackspace hosted email? How good is their web-based client?