I love to make bulletin boards using wine corks. I chose winemaking as my career, and therefore had access to many corks. This is a simple way to use them. I look for frames with good depth at thrift stores, which makes me feel good because it is like putting them to good use again.
I use regular carpenter's glue for the corks, because they are wood, after all. I also use synthetic corks, and for those I switch to a stronger glue, something like E6000 or similar. I tend to pack the corks tightly, so I let the glue dry with heavy books on top, to prevent the corks from popping out.
If you don't work in the wine industry, don't despair! It is easy to get a hold of corks. Apart from the obvious (drink one glass of wine with dinner every night, and you'd be amazed as to how fast those corks gather), you can befriend the waiters at your favorite restaurant and ask that they save you the corks. Do the same with your friends. Or email wine cork companies or wineries and see if they'd be willing to send you some samples!
I have made tons of boards over the years, as they make great gifts. Here are a few photos. These ones are from my private collection.
I took a class called "Wines of the World", and every week I faithfully saved the corks from the wines tasted. They ended up on this board, the first one I ever made. This is also the board by my desk. I cleaned it up to take the photo, but here is where I hang all my bills to pay, stamps, etc. Corks are soft enough that you can pierce them easily with a thumbtack.
This frame was deep enough that allowed for the corks to be placed vertically. I love how they start all aligned, and chaos soon ensues. I don't consider this a functional frame, so I use it as a decorative piece only.
I made this board for my husband when we were just dating. I nailed some beer caps around the frame and glued some tokens, as a way to conceal that it wasn't in very good shape. I rather liked the effect, and have repeated the beer edge a few times. If I find a frame wide enough, I tend to decorate it with stickers. I made a board as a farewell gift for my old boss. I chose wine, grapes, golf, French, and frog stickers in his honor. I kick myself for not having taken a photo before I gave it to him!
This frame was an odd find at the thrift store. The back side is felted, with the days of the week. I thought it would look better in landscape. This is another one of those organic boards where the cork pattern turns chaotic after a couple of rows. I had this board in my work office, and the fact that it is so long was super-useful.