Which camera Lense should I buy for my Canon EOS Rebel XS camera?

Hello..
I’m a total noob when it comes to DSLRs or lenses…so im here asking the expert opinion..
Now..my predicament….
I’m planning to buy a lense for my bro’s Canon EOS DIGITAL REBEL XS camera as a bday gift.
I know that he just started getting interest in photography and has bought the camera..no lenses other than the standard one which comes with the package when you buy it..
I did some research online…and think that telephoto zoom lenses would be a good bet..
My budget range is 200–300$, so these are the 2 of the lenses I found in amazon

1.
Canon EF 100–300mm f/4.5–5.6 USM Telephoto Zoom Lens for Canon SLR Cameras
http://www.amazon.com/dp/B00004XOND?tag=bobatkinsphotogr&camp=14573&creative=327641&linkCode=as1&creativeASIN=B00004XOND&adid=0GFM2238WCKYN5ZWTJ5N&

2.
Canon EF-S 55–250mm f/4.0–5.6 IS Telephoto Zoom Lens for Canon Digital SLR Cameras
http://www.amazon.com/Canon-55-250mm-4-0-5-6-Telephoto-Digital/dp/B0011NVMO8/ref=sr_1_1?ie=UTF8&s=photo&qid=1254010180&sr=1-1

So which one should i buy ??
I have no idea what I should look for in terms of EF/EF-S/IS/focal length/aperture size etc etc

Any help is greatly appreciated.

Thanks again