People mostly use either serif or sans-serif fonts and often miss out the handwritten fonts. They are as important as the main font classifications. I particularly like to use handwritten fonts to highlight significant items in screen captures. They add the personal touch in my design and also provide great typographic contrast. However, not all handwritten fonts are legible. I've put together a huge list of free handwritten and script fonts that work well.
Bee Marker Ink
Bradley Hand ITC (update: not free)
Complete in Him
Freestyle Script (update: not free)
Hand of Sean
It Ain't Rocket Science
Koala (update: not free)