Rackspace offers resellers a partner program to resell their hosting solutions. It includes three tiers, Select Partner, Premier Partner and Business Partner. Their hosting packages are expensive and are better suited for larger companies with a lot of web traffic.
http://www.rackspace.com/partners/
Sales 800-961-2888
Support 800-961-4454
Billing 800-961-4454
Partner Programs 800-961-2888
Rackspace Managed Hosting
9725 Datapoint Drive, Suite 100
San Antonio, TX 78229