Fonts will depend what OS you are using
With most windows versions, you can download them (dafont.com is a great place to get them), unzip the folder and drag & drop them into c://windows/fonts. With vista, it sometimes locks the folder so right click and click install on the font file
Using Save As, choose your file format as .jpg then click Save
and it'll bring up a dialogue box that lets you set the compression/quality level. There will be a little checkbox you can use to turn on a preview in the image window itself.
it needs to be under 30kb
There is a plugin to help save them smaller
http://registry.gimp.org/node/33