JavaScript: RegExp Find
This script is exactly what its name suggests: RegExp Find.
Works much like regular find in browsers, but is JavaScript (Greasemonkey) and supports regular expressions.
One can press (default) Ctrl + Shift + F to Find, Ctrl + Shift + N jumps to the Next match.
Tested in Firefox and Opera.
Related, but different: Beef up the Find command in Firefox - "Greasemonkey script to highlight search entries relative to nearby content."