Text formatting
I recently added a few new text filters for new entries on the system. The one I like best is Markdown with SmartyPants. Markdown enables you to write clean legible entries that are as easy to read as email messages. It then filters your entry into proper XHTML. SmartyPants converts dashes, quotation marks, and ellipses into the proper typographical entities.
If you want to make any of the new text filters (as opposed to the simple Convert Line Breaks filter) into your default for new entries, go the Settings area on your blog, go to the section for New Entries, change the default text filter, and save the change.
Markdown is documented here: Daring Fireball: Markdown Syntax Documentation
SmartyPants is documented here: SmartyPants