When I made the switch to Ubuntu Linux on my desktop computer (that is, if you can call triple-booting Windows XP, Vista, and Ubuntu a "switch"), I was a little worried about finding the applications and tools that would make me as productive working in Ubuntu as I am working on Windows.
After a little searching around the interweb, however, I've been more than impressed with the number of great, full-featured applications available for Linux, many of which outshine their Windows counterparts. And what's best - they're all totally free. Here are my top 10 favorite applications and tweaks that made replacing Windows with Ubuntu a breeze.
Taking a page from Mark Pilgrim's essential software list, I've included the necessary command line code to install most of the applications below; if you don't like Terminal, you can use Ubuntu's very friendly Add/Remove software application interface (Applications -> Add/Remove...). Where I haven't included the apt-get line, follow the instructions in the link.
Full list here: Hack Attack: Top 10 Ubuntu apps and tweaks - Downloads - Lifehacker