I used my 18-55 for quite awhile but the 55-200 was so soft and crappy
that I used it a couple of times and sold it.  I'd check around for
reviews of the Tamron and if they don't sound worse than the Canons I'd
go with it.  My main lens is the Tamron 24-135.

Greg

Get the Canon 28mm f/1.8 prime. Do not pass go. Do not collect $200.

You're looking at some zoom lenses that all have rather sketchy
reputations. Even if the Tamron lens is good "for what it is," what it
is involves a great deal of sacrifice. 6.3 is ridiculously slow, but
even 3.5 is coming near to the limit of even being considered
"all-purpose."

You're an enthusiastic beginner, so trust me when I say that you should
begin as most "enthusiastic beginners" have historically: with a fast
normal prime. You may think a prime lens would be limiting, but in
reality it will limit you far less than a slow lens will. 28mm for the
Rebel makes for a slightly-wide normal lens, literally ideal for street
photography, and useful in landscape applications as well. It is fast
and has quick and accurate USM and full-time manual focusing
capabilities. I had three superb lenses, including some L glass, but
since buying the 28/1.8 a few months back, it has been rare that I've
used anything else. It is fast and light and is perfect to just walk
around town with.

Most importantly, it will force you to make decisions about what you
like to shoot and how you like to shoot. Right now, you likely don't
really know. And though it might seem logical to allow yourself "every"
opportunity by buying zooms, in reality you'll become a better
photographer and learn what you need to get in the future by starting
out with a nice normal and determining where you find that to be
lacking.

I shot for over a year with my first camera and the ridiculous slow
superzoom that I bought for it, despite the recommendations of others.
But I didn't have any "great" photographs until I invested in a fast
50mm prime. You know how I used that superzoom? At its widest, or at
its longest. Now when I shoot with a zoom, I'm picking numerous focal
lengths, not just the extremes. And I'm picking them because now,
finally, I understand what they mean and how they affect my work.

Do yourself a favor and grow into a zoom (or not... primes are great).
Start with a normal prime.

Will

PS: If this is seeming like bad medicine, look into the 35mm f/2.0,
because it will give you similar results (though no USM and lesser
optics) and it is cheap. But give yourself the option of something
normalish and fast (and light), because you'll learn more and be able
to do more.

I have the Canon EF-S 18-55mm f/3.5-5.6 IS USM lens. I leave it on my Camera
as a general purpose lens. It seems to do the job for my needs.

You'll want to decide what area of photography you want to focus on (if you
haven't already, and excuse the pun). If you like close up photography, then
spend the money on a good macro lens. If you like to shoot animals in the
wild, then go for a good telephoto.

I think 18-200 VR bundled with Nikon D50 would be a much better option
at $1200. I always found Rebel XT too small for my hand; since you are
not buying the additional grip (BG-E3 I think), I say you go to the
store to feel the camera first before making any sort of decision.
About DPReview, I have seen bad noisy images from Rebel XT with L
glasses at ISO 1600 in broad daylight as well, so don't let Phil's
studio images be the primary decision makers for you.
On the other hand, 18-200 VR is an excellent glass, been the top seller
in Amazon ever since it became available. You can always upgrade the
body to D200 or something later, which combined with the VR lens, would
be a very good setup.