Any Canon EF or EF-S lens will fit the EOS 350D. This is essentially any Canon lens introduced since 1987.
The brand of your lenses isn't their most important specification. Canon currently offers
more than five dozen different lenses for this camera, but there are a few good ones available from
Tamron,
Sigma,
Tokina and
Zeiss, as well.
When selecting a lens, you first want to decide what focal length or range of focal lengths you need. The EOS 350D normally comes with the EF-S 18-55mm f/3.5-5.6 USM lens in a kit. This range from 18-55mm allows a lot of general photography. If you're getting the camera body alone without a lens, consider the US$440
Tamron 17-50mm f/2.8 as a good quality lens in this focal length range. For landscapes, you probably want something at least as wide-angle as 18mm.
Once you've selected the focal length or range of focal lengths for your lens, look at the maximum aperture (expressed as a ratio to the focal length,
f). Each
f-stop gathers half as much light as the one before it: f/1.4, f/2.0, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22, etc. The EF-S 18-55mm f/3.5-5.6 USM kit lens has a maximum aperture of f/3.5 at the wide end and f/5.6 at the telephoto end of the zoom range. The Tamron 17-50mm f/2.8 has a maximum aperture of f/2.8, meaning that it gathers four times as much light as the f/5.6 kit lens when zoomed in at 50mm. That means that you can shoot with 1/4 the exposure length or 1/4 of the ISO setting.