NOTE: Most of these sites offer music as PDF files, which will require that you have Adobe Reader to view. Adobe Reader is free and is available at www.adobe.com. Click on the link "Get Adobe Reader." Some of the sites also offer MIDI files, which let you hear the music but which require a music editor, such as "Finale" or "Sibelius" to turn the MIDI file into printed music notation.
Werner Icking Music Archive
(This is the biggest and best site. Thousands of pieces are available (not all for recorder). Contributions to the archive are vetted, so the quality of the editions is high.