Input the word free into CNET Download.com search box and up pop over 15,000 results for free software. It would seem to me that everyone knows about the free software at download.com but just in case not I added it here. Download.com is always one of the first choices for finding free software for business.
Be sure to watch what you download. Free may only mean "free trial". Works for me. To try the software before you buy it only makes sense vs. taking it out of a box after putting the cash on the counter only to find that there are compatibility issues.