Sounds like you want to connect a bunch of 120 volt items, but no 240 volt items, is that correct?
I'd first check with the dealer to see if they sell an adapter cable that you can plug into the 120/240V receptacle with something like a power strip with 120 volt receptacles on the other end.
Another option would be to have someone fabricate something, or modify the receptacle, but that could void the warranty, and can be hazardous if not done properly. Check with a dealer for advice first.

You can use something like this splitter:
http://www.amazon.com/Conntek-YL1430520-Generator-Adapter-Connentor/product-reviews/B002MGJ2F4

Note that it still has only two 15/20 amp receptacles for a max of 40 amps at 120V. A 6600 watt gen will provide 55 amps at 120VAC. You will need to balance the load and you can only get 20 amps from each with that splitter. If you want your full power out, you can get it with a splitter for 30 amp receptacles, which is hard to find and inconvenient. Or you can draw a bit more power from one of the other 120V receptacles on the gen, but not more than 27.5 amps total from either winding, so you need to find out how the other windings are connected to the 120V receptacles.