Re: SLR LENS for Antartica 2009!
Paul has given you good advice there. Bear in mind that your Canon 40D gives you 1.6x focal length magnification because of the CMOS sensor, so your 300mm lens becomes effectively a 480mm lens - not far short of the 500mm that you can't justify buying anyway!
Whilst it's tempting to take all your lenses with you on field trips, you would probably regret the extra weight - and changing lenses with gloves on is fiddly. For landscape shots of bergs etc, I'd go with the 17-40mm; for wildlife generally the 70-200mm - but bear in mind that you will probably get to within 5 metres of penguins etc (they have no fear of humans, if you keep still), and so your 24-70mm would be good as well. And your 100mm Macro is a great 160mm-equivalent prime lens that would be excellent for (non-macro) wildlife portraits.
A circular polarizing filter is a must for each lens (it will lose you a stop of light, but that's generally no bad thing in such a bright environment).
Depending on the length of your trip, you might want some more memory / a laptop or portable hard drive for downloads. As for a monopod, I use a Manfrotto - it's heavy but very solid.
One tip I found particularly useful was to bracket the white balance if shooting JPEGs in Antarctica (as you can't play with this very easily in Photoshop afterwards unless you are shooting RAW - and that eats memory cards very quickly!).
I've posted some of my shots in the Members Gallery - these were taken on a Canon 300D with a Tamron 28-300mm lens, so I think they demonstrate that you don't necessarily need expensive camera gear to get good results.
Hope this is helpful - enjoy your trip!