DorkbotPDX discusses looking around for liability insurance for “Maker” activities. thread 
Joe reports, I have two different types of insurance coverage for my business. Thankfully, I haven't had to invoke them, but it's nice to know that I'm covered. I primarily teach hardware hacking classes around the world and design electronics.
Commercial general liability (CGL). This looks similar to what Isaac and Jared mention below. The concept here is to prevent liability in the case of someone injuring themselves (say, while you're teaching someone how to solder) or tripping at the venue where you're hosting a workshop, etc. From what I understand, *personal* liability coverage will not protect you if you're performing business activities.
Errors & Omissions. This is to cover you in the case of unintentionally making mistakes during consulting, product development, teaching, etc. So, preventing the case of "Bob told me to build this and it caught my house on fire" or if you create a product that fails later on and costs a company lots of money. I've found that getting E&O coverage for engineering/consulting can be a bit tricky since "engineering" to most underwriters means "building buildings and bridges" It can be quite costly, too (a few thousand dollars minimum).