Help Choosing a New Lens

[boomstik]

Do yourself a favour and get a fast prime lens. You'll have the world of possibilities open to you. You'll be able to shoot in low light conditions, get great depth-of-field, and practice your portrait skills. A 30mm f/1.4 Sigma is a wonderful lens, and very versatile (I've been using the Nikon mount version for almost 4 or 5 years now, and it's one of my favourite lenses ever). There are two things that make a better photographer: a fast prime lens, and a nice tripod.
The reason I mention 30mm, is that it's wide enough for some landscape work, yet not *too* wide, and fast for some amazing natural light portraits.
If you're more interested in macro than landscape, then go for a 60mm f/1.8 macro lens (again, there's a Nikkor Micro one, I don't know what's the Canon equivalent). This will let you also do wonderful portraits at slightly longer distance, as well as great macro.
If you really do want a wide lens, get a Tokina 11-16 f/2.8. It's very wide, and a lot of fun - not only for landscapes... but it is more limited in its versatility.

To recap: GET A FAST PRIME. You'll thank yourself for that in a year. Plus, a really nice fast Canon 50mm pancake can be found for less than $150 used. Prime lenses GROW good photographers.

PS: I've got the Kata 30 bag, love it.

[boomstik]

Also, you mention you don't like posing people for portraits... Don't! with a fast prime, you can just snap candids without a flash, and you'll find that people come out best in those photos.
So anyway, my recommendation: 30mm (or 35mm, as someone else mentioned), prime. There.