There are a ton of DSLR lenses on the market for a good reason - each has it's pros and cons, you just have to choose which cons you're willing to live with to achieve the pros.
The 18-200 and even the Tamron 18-270 VC PZD could be good options, covering a very wide range. The aperture on those are similar to your 18-55, and they also come with Image Stabilizer, Vibration Control, or whatever the company that made it calls it. The biggest downside, though, is the bigger the zoom range, the worse the image quality gets. So you have to choose a compromise between the practicality of having a single lens, versus the image quality you'll lose.
Another option is to slowly start investing in a series of lenses. The 18-55 is a good starter lens, then if you want to zoom in more, you can get something like the Tamron SP 70-300mm VC USD, or the Nikon 70-200mm, depending on budget. The 70-200mm image quality is wonderful, although the Tamron SP 70-300 is also very good. It also depends just how much you need to zoom in, I personally love the 300mm range, and was even debating just buying a 300mm prime.
Another option is to go wider, such as the Tokina 11-16mm lens.
Finally, you have a series of wide-angle prime lenses, from 16mm to 85mm which offer impressive image quality, and much wider aperture.
If you're really not sure if a lens would be good for you, you always have the option of renting one to see what possibilities it would open. In my first week of buying the Tamron 70-300mm, for instance, I took over 1100 pictures with it, to give you an idea of my enthusiasm. I know I'll love it for years to come. My old canon 75-300mm III, on the other hand, I took maybe 200 pictures with over 2 years, and 90% of them disappointed me (image quality issues).
Cameras: Canon EOS 6D, Canon EOS Rebel T3i, Canon EOS Rebel T2i, Canon S90
Lenses: Tamron: SP 24-70mm F/2.8 Di VC USD, SP 70-300mm F/4-5.6 Di VC USD, Rokinon: 8mm Fisheye cine, Canon: EF-S 18-55mm f/3.5-5.6 IS Lens, 75-300mm f/4.0-5.6 III, and EF 50mm f/1.8 II
Retired camera: Fujifilm Finepix s700