In reply to jmk41:
The DMM ones are good (not the one you have obviously but the other style. Basically a tarpaulin that rolls up into a very basic rucksack. This now appears to have been discontinued but Needlesports have taken the design (first on the page)
http://www.needlesports.com/acatalog/Mail_Order_Ropebags_42.html
I also have an Outdoor Designs one. It is exactly the same but the quality is crap and I have to keep sewing the shoulder straps back on.
I also really like the Black Diamond superslacker, but that is a shoulder bag.