Basically it's free, dead easy to use, and has a great range of effects. I've used it mainly to do collages for the 'ol blog like these:
PicMonkey provides templates for collages and lets you overlay collages or photos with text, or labels like the crumpled paper below
PicMonkey is SO easy to use and I love the collage options it offers! Here is what the dashboard looks like:
There are also a range of photo editing tools that you can use to touch up your photos, or add instagram-ish effects to them. The options really are varied and broad.
I think it adds a lot to photos, so if you have some time to play around with it head on over! Otherwise, have a great July weekend everyone :)
*Full disclosure: I was not sponsored for this post, I just think it's a really good product and wanted to let people know about it!