Here are a few little items that make bookbinding easier:
One day I was browsing through the local craft shop, and in the quilting section found these grid thingies. They have turned out to be incredibly useful in all sorts of ways--I use them for measuring patterns for book covers, the edges for tearing handmade paper to size, for measuring where to put the holes for sewing leather, and on and on. I'm really crappy at math, so these little tools make life much easier!
This is an antique flat iron that I use as a weight. I picked it up at a neighbour's yard sale a few years back, and at some point realized how handy it was for keeping things like leather from scootching around while I am cutting it. I always liked my flat iron's curvy shape, and recently discovered a new good use for it--I use it as a pattern for cutting a nice, rounded edge on leather book covers. You can still find these around at antique shops, but they are getting more expensive, sadly, as people like to use them for decorating. Also, some of them have had a hard life, so are a bit rusty and in need of a bit of buffing and polishing (but then again, aren't we all?).
Finally, here's one of my very most favourite items in my bookbinding studio: my kitschy red pincushion! My aunt made this for me back in the 1970s, from a can lid, some red felt, rick-rack spray-painted gold, and beads. Divine! As you can see in the picture, it is just the right place to keep bookbinding needles :)