I have two lenses for my DSLR. I have the kit 18-55mm lens, and a cheapish 70-300 telephoto lens. Neither one is super fancy. It's really alright since I'm not out to make a living with my photography, just take some fun and pretty pictures and get better. But every time I come up to the coast I wish I had a wider angle lens. The kit lens is pretty good for my basic needs, but photographing the ocean and the redwoods really calls for something better. So I rented a moderate (ok ... one of the cheapest) wide angle lenses for my vacation on the coast. I don't know how I discovered borrowlenses.com, but I love them. In addition to the great tips and photos on their blog, they have a great selection of lenses. This really isn't a review of them or their service, just a quick unsolicited plug.
I rented a Sigma 10-20mm. I'm not too experienced with wide angle lenses or landscape photography. But the best way to learn is just to go do. So I'm doing.