eBay.com has two great deals for the EF 24-105mm f/4L IS USM lens.
New Canon EF 24-105mm f/4L IS USM lens – Authorized Dealer – $675.00 – at Norman Camera via eBay.com
Refurbished Canon EF 24-105mm f/4L IS USM lens – $639.99 – at Adorama Camera via eBay.com
Regular price for this lens is $1,099.00 at most US stores.