As noone has mentioned it you could have a look at Reaper which is a constantly developing piece of software with some excellent features. I chat to a sound engineer on another forum who is well impressed with its features.

It's uncrippled shareware - "REAPER is provided with full functionality, and will not expire after any period of time. We trust that you, the user, will obey the license agreement and purchase a license if use continues."

Supports VST, VSTi and DX plug ins and deals with midi etc