A little while ago, I came to these forums asking what would be an ideal lens for general walkabout usage for my Canon 40D. The general consensus voted for the Tamron SP AF 17-50mm f/2.8 XR Di II LD IF lens, for it's awesome image quality, sharpness, and reasonable price. I happily accepted the forum's advice, finding a mint condition copy of this lens on the TP forums for £240. The previous owner tells me it was just weeks old and had hardly any use; good enough for me, saved me paying an extra £50 for a new one 
I just thought I'd post a fullsize 10 megapixel image up so anyone who's been recommended this and is on the fence about it will hopefully be swayed.
CLICK
Just realised I probably should have posted a photo that hadn't been processed at all, but bah, too late now, can't be bothered
Anyway, all I've done is the autofix for colour, contrast and tone, and added some vignetting.
Anyway, enjoy.
EDIT: I was so impressed with it, I also bought the Tamron 28-75mm F2.8 XR Di Macro, which is equally as awesome, giving me a bit more length and a bit of macro (albiet only 1:3.9 magnification).

I just thought I'd post a fullsize 10 megapixel image up so anyone who's been recommended this and is on the fence about it will hopefully be swayed.
CLICK
Just realised I probably should have posted a photo that hadn't been processed at all, but bah, too late now, can't be bothered

Anyway, enjoy.
EDIT: I was so impressed with it, I also bought the Tamron 28-75mm F2.8 XR Di Macro, which is equally as awesome, giving me a bit more length and a bit of macro (albiet only 1:3.9 magnification).