My favorite software to use happens to be the one I use all day, every day, at work. I am one of the weird people whom enjoy Excel.
An earlier Twitter I gave a link to my RSS Feeds for Excel blogs and the like. One of those blogs that I read almost everyday is Excel Hints. Currently, Excel Hints has a give-away contest going and if you are someone that would like to win Excel consulting or Office 2007, along with a couple other prizes, just go here and subscribe to their Excel Hints email.