In addition to them giving us 5 paid time off days solely for volunteering, I just found out that they will also donate $10 for each hour you volunteer to the organization you're volunteering with (up to 100 hrs a year). I think that's super cool.
At my company, if you spend 50 hours in a calendar year volunteering for one particular organization they will give that organization a grant of $750. I volunteer at a small animal shelter and 2012 is the third year in a row I've gotten that grant.