If you plan on pitching a lot of tarps, go to a camping shop and get a few replacement sections of tentpole (the fancy aluminum kind). They're quite light, and It's much easier than finding sticks every time you try to pitch. If I'm bringing a tent, I bring 3 12" sections, and if I'm not I bring 6.

A u-lock makes an excellent peg hammer.

A shower cap makes an excellent rain cover for your saddle for overnight.

An upside down 2L pot covered with a fleece or a sarong makes a consistently shaped, high enough pillow. (I always had problems with a sore neck from making a pillow from whatever bunched up clothes I had available until I found this trick.)

In cold weather, a thin fleece balaclava can get you from miserable to cozy quite easily.