I get most spam coming to my main personal email address. I've signed up for exactly nothing using it - but other people have sent me ecards (remember those?), shared things from random apps, and/or presumably had their contact lists stolen.

I had always intended to do some analysis of my catch-all address spam, but there's just so little of it that it isn't that interesting. A quick glance through my spam folder shows these have been hacked or sold emails:

Dropbox, Canada Computers, Last.fm

I've also seen a couple forum accounts in the past, but nothing else noteworthy.