The 33-year-old, who has been capped twice, will work as a front-row mentor while assisting in other coaching roles.
Long joined Saints initially on a short-term deal in November 2009 before he was handed a contract until the end of the 2010/11 season.
Long, who previously played for Bath, Munster, Rotherham and Newcastle, has made 22 appearances for the Saints - all of which have been off the bench.
Cambride finished third in National One this season, behind champions London Scottish and Barking, and have set their sights on promotion to the Championship.
Gilbert has released a new line of rugby cleats. The Gilbert Virtuo 8S is part of the exciting new product. Check it out.
The Barbarians are one of the top invitational rugby sides with a long history and classic rugby jersey.
The Nike Tiempo is a solid rugby cleat and one of few styles still made from full-grain natural leather.
The Lions get ready for their matches with this green training jersey. It's what the players wear. Get in the Gear!
A cool looking all black rugby cleat with the high performance adidas is known for. Get in the Gear!
Wear the crest of the British and Irish Lions on your t-shirt. A great look for the summer.
$29.99
The Lions are ready to get their Australia tour underway. They arrive in Perth on Monday.
The New Zealand All Blacks training jersey for 2013/14. Get in the Gear!
The USA Rugby Pro Alternate rugby jersey is perfect for any fan of the Eagles. Get yours to wear during the summer Test matches.
The NEW All Blacks 2013/14 jersey has arrived at World Rugby Shop. Dare to wear the colors of the All Blacks.
