Open Source Office

I was reading Data Smart by John Foreman. I read about LibreOffice as an alternative to MS Office. I am glad I stumbled on it because I just had to shell out some money for a new laptop and was really interested in playing around with data on spreadsheets! I Highly recommend reading Data Smart because it gives you a high level approach to handling data for marketing purposes. Besides the tidbits I am learning with spreadsheet functions, which brings me back to different types of open source software. I am asking because there are a lot of smaller companies in our space who do not have a budget for enterprise level software. What are your favorite open source programs? Particularly, I am interested in seeing what is out there for web conferencing and accounting. Any recommendations? Thanks, Pat