Many DIS-ers swear by
Undercover Tourist. They discount a little, and if you subscribe to the monthly newsletter at Mousesavers.com, there's a link within the newsletter to get an additional discount.
If you already know that you plan to stay off-site,
UT is probably your best bet. If you think you might be interested in getting a Disney vacation package that includes a dining plan, you would have to have a ticket purchase with that.