The Upper Room (of daily devotional fame) has long had a 24/7 prayer line at 1-800-251-2468. They now have a web form for the submission of prayer requests. When you submit a prayer request your prayer is e-mailed to the Prayer Center within 24 hours and submitted to Covenant Prayer Groups. You can submit a prayer by following this link:
http://www.upperroom.org/prayer_center/