I use the windows port of GIMP (free). Still learning it, but it seems to do everything I want. It doesn't do multi-line text, which is the only drawback I've found so far. Many effects are macro'd which is kind of handy. Pretty good range of filters too...
WRT websites, I haven't found any sites that offer consistent free graphics (don't know if free is an issue for you). I like the freedom to design what I want, so I generally do it myself.