Zymol makes an excellent product for that.
About $35 for a bottle though.

http://www.zymol.com/zymolseal85oz.aspx

I have used the full line to detail vans before�selling and they are worth the $.

dylan

________________________________
From: Michael Sullivan <sandwichhead@GMAIL.COM>
To: vanagon@GERRY.VANAGON.COM
Sent: Sun, October 25, 2009 9:45:41 AM
Subject: Rubber Seal Treatment

Good morning, Volks.� Looking for a recommendation on what to use to revive
the seals around dors and windows.� They are in good shape.� Something at
Napa or a home remedy, please.� Gonna wax today.� Thanks.
Michael in San Antonio
91GL AT 'Gringo'
73 Beetle