REAPER is a powerful but sensible Windows application that lets you record, arrange, edit, and render multi-track waveform audio. It provides an extensive set of features, but is a very small and lightweight application (the installer is less than 1 megabyte, and includes many effects and a sample project).

REAPER supports ASIO, Kernel Streaming, WaveOut, and DirectSound for playback and recording. It reads WAV, OGG, and MP3 files, and records WAV files. You can arrange any number of items in any number of tracks and use audio processing plug-ins (DirectX and Jesusonic). REAPER also supports volume, pan controls and envelopes per track, multi-layer undo/redo, and user creatable color themes.

Basic features:
Portable - supports running from USB keys or other removable media
64 bit audio engine
Excellent low-latency performance
Multiprocessor capable
Direct multi-track recording to many formats including WAV/BWF/W64, AIFF, WavPack, FLAC, OGG, and MIDI.
Extremely flexible routing
Fast, tool-less editing
Supports a wide range of hardware (nearly any audio interface, outboard hardware, many control surfaces)
Support for VST, VSTi, DX, DXi effects
ReaPlugs: high quality 64 bit effect suite
Tightly coded - installer is just over 2MB

Editing features:
Tool-less mouse interface -- spend less time clicking
Drag and drop files to instantly import them into a project
Support for mixing any combination of file type/samplerate/bit depth on each track
Easily split, move, and resize items
Each item has easily manipulated fades and volume
Tab to transient support
Configurable and editable automatic crossfading of overlapping items
Per-item pitch shift and time stretch
Arbitrary item grouping
Markers and envelopes can be moved in logical sync with editing operations
Ripple editing - moving/deletion of items can optionally affect later items
Multiple tempos and time signatures per project
Ability to define and edit project via regions
Automation envelopes