Canon has a very wide range of dedicated lenses and is as far as i know the most widely used make of Digital SLR camera.  That is the main reason i went for a Canon camera - there will be people saying Nikon is better for this that or the other reason, but when you are paying so much for a product which is for all intents and purposes going to give you extremely similar results then either will do imo.

So as for make - it is all about the range of lenses and then the "upgradability" of those lenses and bodies which work with those lenses.  Say you want to upgrade to a better camera later on - with an extensive range of lenses you effectively have a "routemap" planned for upgradeability - i have heard that the Olympus lenses - although a rather small range, are superb - but the "L" series lenses of Canon are almost industry benchmarks - but then again you get what you pay for and there is the fact that you pay diminishing returns on quality - increase in price is disproportionate to increase in quality as with pretty much all things photographic.  Anyway, my point is that if i wanted to upgrade my 30D to a 5D or even a 1D then i would only have to get rid of one of the 6 lenses that i own - which is always a good thing.

As for the model - the 400D is a superb camera, as are most other "entry level" DSLR's - the one peice of advice which stuck with me when i was in your situation was to go to the shop and hold each camera you are thinking of buying. I got my 30D over the 350D because i have large hands and the 350D was too small for my grip - plus it was slightly better and i knew it would hold off my wanting to upgrade in the future for a while longer if i really got into photography.  So yes the 400D is a pretty good idea - but if you ware wanting to take macro shots with the SLR you will need to get hold of a dedicated macro lens.

So yeah... that is one person's view on things hope it helps with the decision :)

"In every colour, there's the light.
In every stone sleeps a crystal.
Remember the Shaman, when he used to say:
Man is the dream of the Dolphin"

Rich Meadows Photography