350D Best Everyday/Walking Around Lens

28-300 L, although I don't think "one lens to rule them all . . . " is really practical. I can put together a two-lens kit that'll be cheaper and lighter, cover the same range, and still not be scrimping on quality (24-70 L and 70-300 DO IS). If we restrict ourselves to a "lens for everyday carry, when you don't want to take the whole bag", I'd say that the 17-40, 17-85, 18-55 or 24-70 would all do fine. Let's not forget that the 24-70 on an APS-C gives the same coverage as the lenses on Canon's PowerShot A series 3x zooms and that's plenty for most folks day-to-day.

i hike with either the tamron 28-200. or the canon 28-135mm is lens!
love that is though.
-zacker-

When it comes to lenses StealthLude has excellent taste
On all other things I reserve judgement.

A lot depends on whether you are expecting in the future to change to a full frame camera. If not, the 17-85 IS, which is EFS fitting for small sensors, is fine. Otherwise, you should consider a FF lens like the 17-40 f4L for your 350D, as it could be a better longterm investment.