Reaper is a free DAW (Digital Audio Workstation) for PC, Mac and Linux. It does prompt you to purchase it for $60 (or $225 commercial license) but it will also allow you to hit the "Still Evaluating" button indefinitely.
The company Tracktion has a free DAW called Waveform. Previously their free version was T7, but now the most current version (v11) is free with an upgrade to Pro costing $119. Waveform Free is basically unlimited (track count, importing and exporting).
If anyone is keen to check out an essentially free DAW check out Ardour. Its pretty decent in terms of features and its efficient for editing. It also allows a wide variety of plugin formats including LV2 which is pretty sturdy. One of the first DAWs I'm aware of that works on linux and its completely open source! Its essentially free but you're expected to donate, so pretty much a pay what you want. For $1 it can't be beat really.
Recently version 6 has been released and seems to have been completely re-engineered from the ground up. Not a better time to try it out.