I wasn’t really aware of the differences behind the S and the L in the Canon lens nomenclature, but thanks to Rasmus for pointing it out, and thanks to Wikipedia for all the gory details. Here’s where you can read up on it all:

• The EF mount is what all modern Canon cameras use
• The L-series lenses are described in the same article, but further down
• The EF-S series has its own page, because it’s a separate mount: You can use EF lenses on the EF-S-compatible cameras (the small chip bodies like the 350D and 400D), but you can’t use the EF-S lenses on the full-frame bodies like the 5D and 1D.

There’s also descriptions of the individual lenses in question:

• 24-70mm L, which is a great L-series lens
• 16-35mm L, which is a really expensive L-series lens
• 17-40mm L, which is a more affordable L-series lens
• 17-55mm EF-S, which is a decent all-round lens

Fredmiranda.com also have some good reviews:

• 24-70mm L
• 16-35mm L
• 17-40mm L
• 17-55mm EF-S

I can’t find one for the 17-55mm one.

For the record, I ended up getting the 17-55mm to take along when I travel and only want to carry one lens. Usually what I want to do is capture special moments and glimpses, and I’m okay with trading some quality for convenience. But I’m going to take Rasmus’ advice and keep the 24-70mm lens. It’s too good to let go of.

Some of my latest photos are taken with the 17-55mm.