Which lens should I buy for Canon Digital Rebel XT (EOS 350D)?

You've listed the best first (which is also my recommendation): Canon EF-S 17-55mm f/2.8 IS USM Lens

The key here is that it's an f/2.8 for the full range of it's zoom. The other lenses with the range of f/ numbers let you know that you begin to loose light as you zoom in.

It would be helpful to know what lens you already have, what you plan on shooting most (landscapes? portraits? events?) because of each these might cause me to recommend another lens all together.

But for an all-around lens, the Canon EF-S 17-55mm f/2.8 IS USM Lens is the best of what you've listed.

The EF-S 17-55mm f/2.8 IS USM is a very good lens, as is the EF 17-40mm f/4 L USM.

The EF-S 17-85mm f/4-5.6 IS USM is no way near as good as the other two and it would be far from my choice of lens.

I would also choose the EF-S 17-55mm f/2.8 IS USM as the pick of the three. All the reviews I have read have been very favourable. It has IS, it's fast, it's almost L quality. It's only real downside is it's high price and it's lack of weather sealing. But I would definitely buy it (if I could justify the cost).

check out the review sites below...

OK this is contraversial. I wouldn't recommend any EF-S lens. If you want a lens that will outlast the camera, then this is possibly unwise as the cost of full format sensors is coming down and it's only a matter of time before the S series is redundant.

I have a Canon 40D and use a EF 28-135mm f/3.5-5.6 IS USM lens as my day to day workhorse. I have other lenses but this one has such a wide useage and has been giving some excellent quality.

If the reason for considering an S lens was to get a the focal length down you would be better off buying a prime lens. The 50mm f/1.8 II although very basic is superb and cheap. True the focal length is really 80mm given the 1.6 factor for your sensor, but for blurring backgrounds on portraits it's great. Alternatively go for a shorter focal length, although it will cost more.

The L series are undoubtedly the best but very expensive.

Good luck

Phil

I see that you are particularly interested in the wide to normal range of focal lengths (really, a standard zoom, giving the same range as your standard 28-70mm in digital), if that's the case I recommend the first on your list, the EF-S 17-55mm f/2.8 IS USM for its constant maximum aperture of f/2.8 throughout the focal range. IS helps as well. The closest thing nikon has to that lens is the AFS 17-55mm f/2.8 DX and it doesn't have VR (IS) AND costs $1200. From what I've read of it, the canon version is highly acclaimed and a great standard zoom for crop cameras. The same is true really for nikon, but I wouldn't get it. I'd much rather have the 18-200mm VR which for me would cover that range, and then some and the VR would make up for the lack of having f/2.8 as a maximum aperture. That's me though.

canon EF-S 17-55mm f/2.8 IS USM lens sounds good considering you're into landcapes and portaits. on the wide side, this lens is perfect for landscapes. f/2.8 will also be very useful for blurring out backgrounds when you're shooting portraits. the is would help a lot in both instances too when you're shooting in low light.

Of those three listed my advice would be the

17-55mm f/2.8 IS

It is fast and you will really utilize the IS feature.

The L glass would be a great lens too.

Look ahead at the current cameras made by Nikon and Canon. Once you buy a specific camera system, you will be married to it for a few decades, so take your time and do the research on those two brands. You have to ask yourself. Are you buying for image quality or for price?

none of the above... try sigmas 28-300... its a great lens