Sound Valley:
Sound Valley is a free utility which was created to bring the sounds of nature (birds singing, wind in trees, forest stream, rain, storm, etc.) right onto your computer. You can choose from the included scenes the one you want to listen and configure its playback options.
Sound Valley allows you to select the scene duration, play order and it also has some useful options like Sleep Timer and Rest Reminder.
Installable version: soundvalley-2.3.1.157.exe (32.7 MiB)
Portable version: soundvalley-portable-2.3.1.157.zip (29.0 MiB)