Blurring faces for anonymity

[mitcham]

I am fairly new to OCC and I haven't really found my way around yet, so please forgive me if I've asked this question in the wrong place.
I've got a lot of interesting pics - piercing, see-through, etc. - of my wife and various friends, that I'd like to post, but they need the faces blurring to protect their anonymity.
I'm not too clever with computers and I need a free program download to do this with. Can anyone suggest one that's simple to use?
Thanks in advance for any help or advice that's offered.