I second the recommendation for
www.undercovertourist.com. UCT is an authorized re-seller of Disney multi-day tickets that they offer at a discount from the Disney prices. They will mail your order to you very quickly to addresses in the US, Canada, and a few other countries at no additional charge. Excellent customer service on any issues with your order. As the previous poster mentioned, if you go to
www.mousesavers.com and sign up for all the newsletters/notices you'll get a monthly email that typically includes an additional (slight) mousesavers discount on ticket prices. Their quoted prices include tax, which isn't always the case when buying tickets from other agencies (and surely isn't the case when buying directly from the Disney ticket website).
In my experience this company has produced the lowest, no-strings-attached pricing for WDW tickets over the past several years.
Dick Taylor