Personally my preference for this is a UML deployment diagram, identifying the servers concerned with the sources, destinations and package(s) used.

There is a tool available calles SSIS Documentor which integrates with BIDS, I've not got round to giving it a look, it's got an evaluation version available so you can try before you buy http://www.ssisdocumenter.com/download.aspx

another option thaht may be worth looking at is http://www.pragmaticworks.com/products/business-intelligence/bidocumenter/default.aspx