Shoe Goo has always been part of my repair kits.

http://www.bootrepair.com/goo.htm

It is great for gluing back on a sole or filling in a hole or worn spot. It is a good adhesive which will stick to any thing and a good filler material which is very resistant to abrasion. It is not only good for shoes/boots but I have used it for all kinds of things were a glob of sealant, water proofer, filler or adhesive would do the trick. Kinda like liquid duct tape.