You can't go past the 17-85 IS. Cheap, sturdy and sharp. I've used it primarily in urbex photography - with some landscape, portraiture and night as well - and it still works as well as the day I bought it, even though I've hit it on numerous ladders and metal things (so clearly it should be fine for all your travelling needs!). The image stabilization is incredibly useful too. Here's a link to some photos I've taken with the lens:
Flickr: tokicat's stuff tagged with 1785