If you don't have a website, or even if you do, there are a selection of websites that allow you to host a gallery. This allows people to find you on those sites, and gives you a place that you can send people to if they want to see an example of your work.

Here's a (surely incomplete) list of some sites that are worth checking out:

CGHub - the prettiest in my opinion
DeviantArt - possibly the biggest one around
CGSociety - Lots of computer game art and 3D modelling but a decent amount of 2D stuff too.
ConceptArt - Another huge CG community. You can host a gallery there, and post a portfolio in the portfolio subforum
Elfwood - specifically a fantasy art forum. I had ignored this, but I just picked up a commission from there, so it's worth putting a gallery up.

These are a quicker and easier alternative to setting up your own website and they are a useful way of increasing your visibility. Chip in if you have any more that you've found useful.