Make your own parts
From the this is just plain cool department: eMachineShop allows you to design any physical "part" you want using a CAD program you download and then submit the plans to them. They will machine the part using any number of processes and ship it to you. You can do quantity one or 1000s. You can use just about any material you can think of.
Now I gotta think of some project that would require me to make a part so I can try this out!