Here's the ultimate vacation kit.
http://www.dpreview.com/reviews/specs/Canon/canon_sd500.asp
Coupled with a 3gb mini drive and a couple extra batteries.

This is one you'll always have on you, even if you're just going out to
dinner, unlike the big heavy 20d.  The best photo is the one you don't miss
because you left your camera at home. :)

Speaking now from a bit of experience, I'd suggest you get two lenses,
maybe three:

The widest angle lens you can find.  Wide angle turns out to be a tall
order on these 1.6:1 cameras.  You mentioned your motivation of
photographing scenery.  You need wide angle to do landscapes and
waterfalls and so on.  I've been frustrated even with the 18mm end of
the 18-55 kit lens (which feels crummy, but does not perform badly).
I'm now in the market for something like a 12mm prime, and I want a
really, really good one.

Then you probably want a 200mm prime.  For those situations where I
think I want a zoom lens (birds), I'm realizing that what I really want
is just the long end of the zoom.  And a prime will certainly be much
better than a 70-200 zoom at 200mm.

On the other hand, the IS zooms are really great lenses.  People are
getting results with a 20d and an "L" zoom that are good enough for any
pro quality standards.  [They'd better!  A 20D and an L Zoom is a $3000
camera!]

One lens you would probably enjoy having is the 50mm f/1.4 (NOT the
f/1.8!)  It is a great lens; the only one I have so far that I actually
consider to be very good.

I have a Tamron 28-200mm zoom.  It's not at all good for wildlife or
birds, very soft at the long end.  But at moderate lengths it's pretty
good!  Definitely worth the sub $300 price.  (I know I need and EF/L
zoom, but that's not going to happen unless you buy me one.  So I'm
working with the lenses I *can* have.)

There's another issue that you might want to consider.  You can get so
*close* to great results with these cameras, that you may end up being
frustrated to the point that drives you into the medium format film
world, or worse.

I've seen guys show up at several places I've visited this spring with
their hassy's and so on, and once even shot a lighthouse after waiting
for a guy to do one with his field camera.  (He was quite quick about
it, it was impressive.  I think there must be something very satisfying
when you take your shot with your view camera and you have good
confidence that you got the exposure you expected.

Oh well...

As for tripods, I'm really happy with my Velbon GB347.  I'll be in the
market soon for a carbon fiber tripod with a ballhead (something that
substantially contributes to the cost of the $1600 zoom lens I'm
looking at!), but the Velbon is pretty nice, and plenty portable, it
doesn't encumber me at all, even on fairly difficult hikes.

One thing I'd consider also, as an "accessory" to your 20D, is a small
Canon camera, one of the  better Powershot models.  They are very high
quality, and in some situations have performed better than equivalent
photos taken with the 20D (which is a bit disturbing).  Canon
point/shoot cameras have quite similar exposure controls to the SLRs,
so they translate well.  

Gotta go board my plane, right now.