Check out this list of links to over 450 free downloadable vector pattern swatches compiled by designm.ag. Includes seamless patterns, plaid patterns, batik patterns and more.
Many of the patterns are also available as JPEGs, so they can also be used in other programs. (Illustrator is still the best way to set pattern swatches up and get them looking exactly like you want. Hey, this is an Illustrator site, what do you expect our opinion to be!)
Click here for the list of links.