ebay seller deals-all-year has a 99.8% positive feedback rating on ebay. The listing notes that you can register this lens for a 1-year Canon USA warranty.
ebay (via 6ave) has the Canon EF 24-105mm f/4L IS USM lens for $639.99 (reg. $1149). Check it out here on ebay.
Note, this is likely a grey market item with an in-house warranty from 6ave, which has a positive feedback rating of 99.3%.
[UPDATE: These are all gone now at the deal price now. It's back to $1149.]
ebay (via Adorama) has the Canon EF 24-105mm f/4L IS lens refurbished for $639.99 (compare to $1149 new). Check it out here on ebay.
B&H still has the killer deal on the Canon 6D with 24-104mm f/4L IS lens for $1999 (reg. $2499). Check it out here at B&H Photo.
The new Sigma 24-150mm f/4 DG OS HSM lens is now in stock for Canon DSLRs. Check it out here at B&H Photo.