Sigma 70-300mm f4-5.6 DL macro (Canon) for $112~
The Sigma 70-300mm f4-5.6 DL macro lens (Canon EF mount) is offered for $112~ with free shipping at Amazon by Amazon itself. Only the Canon mount is discounted thusly.
Please note this is an older lens. It is not stabilized, not APO, not DG. Jack Proton pointed out in the comments below that this lens may give you error messages with Canon DSLRs (see comment below for more).