Social recommendation service StumbleUpon is celebrating Mother’s Day by offering the chance to win a $100 Amazon gift card for being the Coolest Mom on StumbleUpon.

To nominate your mom for the prize (she can also enter the contest herself), you can tweet a link to the Stumbler Mom’s profile using the #StumbleUponMoms hashtag or comment on the “Coolest Moms on StumbleUpon” post on StumbleUpon’s Facebook Page with a link to the Stumbler Mom profile you would like to nominate. The contest entry period closes at 11:59 p.m. PDT on Sunday.

The winner will be determined through a random drawing and the winner will be contacted next week. You can check out the terms and conditions of the sweepstakes here.

It’s a cool little giveaway, and acts as a little reminder that it’s not only teenagers and twentysomethings who use social networking services. Meanwhile, if you’re struggling for ideas on what to get your mom on Sunday, you can always hit the Stumble button and grab some inspiration from the Web pages you discover through StumbleUpon.