Scriptalizer allows you to type in whatever you want and it will give you the look of a hand written note. You can play around with different styles of handwriting. The easiest way to get your writing onto a GIMP file is to take a screen shot first. Then import it.
Postergen.com allows you to create various fonts including a chalkboard style of writing. Again, to avoid paying the 14.99 for the image. Just take a screen shot.
This website is a fun way to create a graffiti like tag. You can play around with different fonts, colors, flare etc. This site is free so you can either take a screen shot or download your image. Sometimes this site is very touchy so don't get too frustrated if something gets glitchy.
Word cloud allows you to type in or paste a list of words, choose your colors and fonts and it will jumble them up into a random assortment. This might be a good option for those of you who are looking to have your text element be more of a background texture.