The 28-135 has been mentioned, as has the 24-105. I have both.
The 28-135 is cheap and cheery. It has a similar trombone zoom as the 24-105, but unlike the quality build and feel of the 24-105 the 28-135 has sideways slop and feels relatively cheaply made. It also suffers zoom creep - big time, where I have yet to notice any creep on the 24-105.
The IQ difference is quite noticeable, but mainly when viewing images at 100%. You look at the 24-105 and think yep, that's not bad, you then do the same with the 28-135 and think yuk, that is soft! Processed and shrunk down for the web though both are pretty good, with the edge going to the 24-105. The 28-135 gives great colour and contrast though, I find it the best for things like flower or vegetation shots. Don't get me wrong, it can deliver great shots, I have taken some beauties with it, but I rarely use it these days though and will get around to actually getting serious about selling it one day.
If your budget is really tight I'd say go the 28-135 and just work slightly harder in your processing, if you have a bit of leeway I'd say go the 24-105. Both will fill the range you are looking for.