I came across a fellow assplay bloggers site today that has a great description of how to make your own dildos. I have often wondered if it was a difficult process, but, after watching the process on video and reading the description on Up My Bum (site no longer active), I am surprised how simple it can be. Basically, all you need is food grade pure silicone (easily available online), some sort of vessel you can cut away, a bit of mould spray or cooking oil to stop the silicone sticking, and with a bit of ingenuity you have your own homemade silicone toys. The toys below were made using this process. Not sure what the first one was made in, but the others using a POM bottle, and a Fanta bottle.
You can watch the video and read the directions at Up My Bum (site no longer active).