there was a recent thread on card speed where i posted a link
http://www.steves-digicams.com/high-capacity_storage.html
that said the rebel xt doesn't handle the really fast ( pro type) speeds so it would be a waste of your money. i have a 130 speed card and some 60 speed cards that i use most often ( 1 or 2 gb)and they all seem about the same to me in my rebel xt.
he mentions another site where you can compare card speeds that was also posted by( i think) bob q on that other thread... perhaps way more than you want to know

but you can use the scroll to get to your camera if you want . there is an atp card listed if it's the same one.( bout 1/2 way down, a few past the dark blue)
http://www.robgalbraith.com/bins/multi_page.asp?cid=6007
i also have two of the same as the slower ones mentioned there( simple tech, 2 gb/512 mb) also and i can't really say i've ever had a problem except it might seem a little slower downloading to the computer to me t . i haven't had the need to do a large continuous mode ( i've only taken probably 5-6 shots in one, max burst is 14 large/best quality, although it also says a faster card will give more burst shots ) but so far none of the cards i have, cheapie or not, have been to slow to work fine at that. just fyi i know the rebel book mentions if it seems slow in coninuous drive it could also be a low battery.
if you have a nearby micro center they have 1 gb micro center's sd bulk cards for $15 fairly often ( the salesman said they were 60 speed) that i have and use a lot...they have worked fine. ( see below about the converter for sd to cf)
naturally you can spend more but since i have dropped them a number of times already, i figure since they are still working they must be sturdy enough.
also if you have a previously used sd cardfrom another camera, you can get a converter to use it in a cf camera...i got one for around 20 on ebay that works fine with my sd cards plus that way i can "borrow" my kids sd cards for vacation
edited cause...I tried the burst mode with the cards i have( dd has my fastest one). the results of my unscientific to much time on my hands research

was...... simple tech,2 gb= 96 photos before it slowed down, then the busy went away within a fraction of a second..simple tech 512, about the same( lost count at 87 when the phone rang but it kept going after that for a while

), micro center sd in sd converter, 1 gb, =49, till it slowed down as above, san disc sd utlra, in converter, =38 pics till it did the above.
not sure how long expedition everest is but i would guess you could take a lot of the ride without even pausing,( not to mention if your finger got thrown off the shutter button due to motion, fear, shaking what ever

) then the brief pause and reshoot. can't really think of to many other places i'd take 100 pics in burst
