Holly and I both love collage and old books, so we love the idea of our altered art swap books! Basically we have two, which we add to and then swap back and forth, so each of us always has one. We've come up with some pretty awesome page spreads (see below for a few of them!) And I've created a blog that is just for photos of these books here called Yellow Hammer.
Each book is titled by the last one or two words in the book. Eg. "Yellow Hammer" and "Adversity". (No idea why those are the last words in a book - very odd - mostly they come from the index which is last is some of the old books)
To keep them looking interesting and because of the cool yellow aged paper, we use small old books we pick up at second hand stores.
Basically anything goes. Pens, paint, acrylic, watercolor, cut-outs, stickers, decals etc. Whatever can fit inside the book is fair game. I have a giant wire basket I toss anything that looks interesting into and that's my pile of creative ideas. Use lots of glue so they don't fall out later, and staples are another favorite adhesive.
Below you can see a few of the pages we've done. As you can see we use a variety of styles and ideas. Whatever happens to sound good at the time. We each do one or two pages before passing it on, and they can be singles or two-page spreads.
Be creative and have fun!