The lenses you select will be highly dependent on the types of shooting you will do as well as your budget. Several choices have to be made:
-- zoom lenses (with variable focal length) vs. primes (fixed focal length) - normally primes have better optical quality but you trade off some capability by having to 'zoom with your feet'
-- Professional grade vs. Consumer grade - Canon L series lenses are superb - but can cost thousands of dollars - so the deciding whether you can afford the quality and build of a pro grade lens is a descision to make
-- Canon vs. other brands - Sigma, Tamron and Tokina all make EF mount lenses and normally sell them for less (e.g. the Sigma 70-200 F2.8 is almost half the price of the Canon version)
As you think through these things - you might not really know what you want yet, so there are certainly some good starter lenses to consider:
The kit lens that comes with the 350D is actually a pretty nice lens - if you have this - you have a nice consumer grade lens that will go fairly wide (18mm) and also has a mild zoom (55mm) - you could use only this lens for awhile and this will give you some clues to where you need to go next (not wide enough - look at the EF 10-22, not long enough, the EF55-200, frustrated with quality...look at L glass or primes).
Beyond that - here are some typical first lenses to consider:
50 mm 1.8 - plastic fantastic...cheap, sharp and a must for every bag
10-22 EF-S - sort of pricey and there are some alterantives from Tamron, Sigma and Tokina but a pretty nice little wide angle
28-135 IS - a good mid length zoom - nice walk around lens
Tamron 28-75 xrdi - F2.8 so it's fast - optical quality is a excellent and the price is right - another good walk around lens
75-300 IS - a good first zoom...and the IS is great
70-200 F4L - normally the first L glass many people get since it is not that expensive ($560) or so
Once you buy L glass - you are pretty much doomed and will probably drain your kids' college funds buying more... :)
I posted some links below where you can look at samples from many different lenses or see testing of optical quality. Have fun!