Flame* is "a painting program, it belongs to my 'I am Artist' experimental project. I think with tools which inspires you, everyone can be an artist. You can try it here, change different brush settings and paint your own flame paintings. When you change background from black to white, palette changes from additive to substactive and the feeling of the painting is very different. It's not easy to explain all brush parameters, so I leave this for your experimentation."
I made this cover (cick image to see larger version) for one of my poetry books with Flame, and I think it ranks right up there with Dreamlines as an inspirational online art tool. You do have to play with Flame a bit to get a handle on the different settings, but they're fairly easy to figure out. This is not a generator for control freaks, btw, but if you're into abstract and fluid art you'll quickly become addicted.
I've also just started playing with the online Font Image Generator to manipulate some text for different applications like banners and other blog bits. This one might be good to make small projects like banners, avatars and icons, like this one:
Someone (you know who you are) asked me if there is an online graffiti generator with colors and effects that you could tweak, and here's one I just found: the Graffiti Creator. I used it to create bookmarks for a kids' literacy event (see below) and a header for a school workshop handout, and while it also requires some time and experimentation, it's also pretty simple.
(*Link filched from Gerard at The Presurfer)