empty prescription bottles work well too.
A piece of batting on your lap seems to attract loose threads.
That rubberize shelf liner that you can get in the housewares section of Walmart is great for keeping your foot pedal where you want it and for keeping your machine from walking across the table.
Last year on a garage sale I purchased one of those metal record album holders from the 50's or 60's and it works great for holding my rulers.
I'm off to a garage sale this morning to see what kind of bargains I can find---I'll let you know if I find any good ones. They advertised quilting supplies and fabric. I'm still searching for a couple more record holders--my two quilting sisters liked my idea so much that they want some for themselves. And there's been so many good ideas on this board that I'm going to really keep my eyes open.