[Rover]

There's a wealth of options right now for (almost) every budget. The 28-105 looks pretty fine stopped down to f/5.6 (<70mm) or f/8 (70mm+) - see this evaluation http://www.the-digital-picture.com/Revie...eview.aspx so you might want keep it for awhile. A few wide and tele lenses of note:

Wide (roughly from least expensive to most expensive; depends also on how wide you want to go):

Sigma 12-24/4.5-5.6

Tokina 17-35/4

Canon 17-40/4L

Tokina 16-28/2.8

Canon 16-35/2.8L II (I have this one; it has a couple of quirks but is otherwise stellar. Comes with a price unfortunately)

 

Tele (same routine):

Tamron 70-300/4-5.6 VC USD

Canon 70-200/4L IS

Sigma 70-200/2.8 OS

Tamron 70-200/2.8 VC USD

Canon 70-200/2.8L IS (either version; I'm using the first one and can't praise it enough)

 

Standard zooms that might eventually replace your 28-105 if need be:

Tamron 24-70/2.8 VC USD

Canon 24-70/4L IS (has 0.7x macro)

Canon 24-70/2.8 (either version; the second one is mega-expensive and has no IS)

I have the 24-85/3.5-4.5 lens in this niche and it looks much nicer than the 28-105.