I started getting rid of old school work from grad school (school is a hobby, but keeping old papers isn't) and I also realized there's no good reason to take up space and collect old pictures.
I also gave away what was left of my stamp collection and gave away the second half of my coin collection. I had all common types so it wasn't worth trying to sell anything.
You could call me an anti-collector and if anything I want to collect, it's more free cubic footage in my living space and I am not about to be able to afford (or size up even if I had all the cash in the world) and enter the still dangerous world of real estate.
So I am doing the best thing for now which is getting rid of all collections which are pretty much nothing more than clutter with a fancy name attached to it. I also think in these times, while it may sound boring, it's good to save for a rainy day and/or pay off debts.
For those who collect things like MP3s, diplomas, or downloaded internet movies and tv shows, they don't take up a lot of space and won't clutter the house and seem to be common things people pursue these days. I think collecting works my worst part of my addictive personality so I don't collect, even the MP3s, and it was only last year I started using iTunes and that appears to potentially be the most addictive thing in our society as far as buying stuff (thus Apple Inc's great rise with devices and downloads).