My Honda EU3000 generator has two types of output receptacles. One takes a usual (USA) 3 prong 110v plug. The other is also 110v but seems to take some type of twist connector. I need to find an adapter to change it to the usual 3 prong plug. What is this twist connection called and are there adapters to standard 3 prong plug type?
Just what you asked in your question. It's called a "twist lock" receptacle and accepts a twist lock plug. You will find this type of plug at the temporary power pole on job sites. They have the distinct ability once plugged and locked-in the receptacle to remain plugged-in no matter how the extension cord is pulled. This has saved many foot steps back and forth to re-connect for power.
And yes you can buy change over adapters that have a male twist-lock and a 3 prong standard female plug at each end.
With your help I learned that the twist connector receptacle on the generator is an L5-30 and the regular 3 prong 120v outlet plug is called a 5-20. So I ended up getting this adaptor: http://www.zoro.com/power-first-cord-adapter-20a-l5-30-5-20-4fzz2/i/G0860334/