I was just munging some data from Excel into a web page to document a data structure. Started by cutting and pasting into Textmate and replacing tabs with the HTML I wanted to show there using find and replace. Then I wanted to add a break to the end of each line. A couple of seconds Googling came up with this. Anyone with textmate should give it a try - it's very cool to see your keystrokes being replicated over fifty lines - brought the sorcerers apprentice to mind (maybe I'm just too easily amused)!
What else do you do to improve your general efficiency? I'm thinking I really owe it to myself to make more use of grep and similar Unix tools, to learn RegEx's properly for everyday text search and replacements and to check out the Automator capabilities on a Mac (lots of scripts available. What are the little productivity tweaks you've made that add up to useful savings over the months and the years?