The easiest and cheapest is definately DPP and EOS Utility though me personally have found EOS Utility to be a bit easy to crash especially with the 40D and 450D cameras. May just be my crappy computer though.
There are however other options which can be found on this forum (i think) but i'll run them through real quick.
EOS Utility for capture, Lightroom for viewing:
You set the EOS Utility to capture to a directory, and then have Lightroom watch that using the Auto import feature. A bit slow but you get your photos directly imported into lightroom with all the nice perks and viewing features of that.
Capture One 3.x Pro
Expensive, but if you have a 5D this is a killer solution (afaik as i unfortunately have the unsupported 40D & 450D when it comes to tethered =). Same functionality as you will get with Lightroom in terms of viewing and organizing but all in one package. Quite nice way to present the images aswell and the raw conversion is great.
Bibble Studio Pro
Haven't used this much but some users like it. It also has direct tethered support for the 5D and viewing and organizing in the software making it easier to show directly for your clients.
Breezesys DSLR Remote
By far in my opinion the neatest solution and the one i went for (especially when capture one is doing the old osterich technique with tethered support right now
. It handles all Canon DSLR's and will do everything EOS Utility will do for free but reconnects more gracefully than the utility and have built in viewing directly in the software. I opted for this as i wrote before and i use it to evaluate the picture directly and also let the client see the results.
This software however wont rank your images (afaik) so letting the client select directly through it may not be the best option. I think in that case that the previous ones are the better solutions.
Hope this gives you a few more insights in what options there are. And if anyone have any other software/options feel free to share them.
/Henrik