Bit of a pain trying to get my default format filters in the right order. Here is what I finally came up with:
# Textile - wiki syntax -> xhtml converter. Needs to go 1st.
# URL filter - convert text urls to clickable links
# HTML filter - remove dangerous html elements
# Code filter - do syntax coloring of code blocks
# Line break converter - convert text returns into html paragraphs. Textile tries to put in br's, but the HTML filter pulls them back out.