REAPER is a powerful but sensible Windows application designed for the recording, arrangement, editing, mixing and rendering of audio. REAPER provides a flexible but easy to use interface that is equally suited to amateurs and professionals alike.
REAPER highlights:

Extremely small footprint
REAPER is full featured, but its installer is barely over 1 megabyte. It starts and closes fast, and is easily installed on new systems or on portable drives.
Easy to use
Simply drag and drop one of many kinds of files in to edit existing material, or insert a track and arm it for recording. No complex project or definitions to set up.

Fast and powerful editing facilities
Split, resize, fade/crossfade, pitch shift, timestretch, copy/paste and loop media items with ease. Ripple editing is available, too.

Unrivaled routing capabilities
Send tracks to any number of other tracks or hardware outputs, with lots of options (pre-fx, post-fx, independent faders, mono or stereo). Not interested in advanced routing? You don´t have to use it (and it certainly won´t get in the way.)

Powerful recording options
Supports pre-fx, post-fx recording, can record mixed output of multiple tracks, etc, supports switching record inputs/modes on the fly, input monitoring options (including tape-style auto input monitoring mode), supports auto-punch-in/punch-out, and more. If you want. Otherwise, it just behaves as you would expect.

Wide open compatibility
Sane, human readable, human editable project file format. Support for reading and writing many common file formats. Support for consolidating track edits and rendering track stems, to enable easy export for other applications. EDL import/export for Samplitude and Vegas.

MIDI support
Support for MIDI files, recording MIDI, and VSTi/DXi softsynths. MIDI can be integrated and mixed with audio.

Customizeable user interface
User arrangeable user interface with color themes: make REAPER look how you want it to look, and arrange (or hide) elements of the user interface to suit your needs.

Bundled Effects and 3rd party plug-in Support
Includes built in effects including a compressor, gate, FFT EQ, and some basic synthesizers, and includes many Jesusonic effects, and supports many plug-ins (including VST and DX plug-ins) with full plug-in delay compensation.

0.99 is the last freeware version of REAPER, starting with version 1.0 the license was changed to shareware.