I created integrations with ExactTarget for a client and found it was an up-hill battle to get information about their web services and rest interface.  The only way to get the documentation is behind lock and key, a private forum and knowledge-base called 3sixty that is slow, has no user participation, and if you are a freelancer it’s just another layer of overhead to get an account to talk to people there – probably the reason why there is virtually no user adoption.  :)

Since I see no merit in contributing code to a private forum that you have to buy in for the sake of that company, I bought a domain and put up a punBB forum to give people a public space to talk openly (like the Salesforce.com forums):
http://ExactTargetDeveloper.com