The following sources are ones that I have used. You should check the conditions of use, and copyright status of each piece and each site yourself and ensure you comply.
If you know of any other sites that should be included here, please let me know by email at email@example.com.
International Music Score Library Project - A cast qauntity of public domain music for all sorts of instruments and groups, in facsimile and arrangement. Search by keyword, download and print as required.
Dolmetsch - Some free music, some chargeable. All for recorder ensembles of various sizes. Lots to explore.
Mid-Peninsular Recorder Orchestra, based in California. Frederic Palmer was (is?) the director of music there and has composed a large number of pieces, both original and arrangements, that are very playable and of excellent quality. For various ensemble groups.
Web Library of Seventeenth Century Music. All kinds of music from 1600 to 1700, much of it playable by recorders, either solo or ensemble.
Free-scores.com - A French website with quite a lot of free sheet music, arranged for various instruments and combinations. Your browser might help you translate the pages, if your French isn't too good! Also useful to know that "recorder" in French is "flute a bec".
Serpent Publications - "Play music the way the Elizabethans did".
Floetennoten.net - A German site, but this is the English language version. Contains a useful amount of recorder and flute music. Most of this music is not free, but it is very cheap. Prices are in Euros (1 Euro = approx. NZ$1.70). You can preview before you buy. When you buy, you download .pdf files.
Lyrischesuite - A Japanese site, home to the Aeolian Recorder Ensemble, that contains quite a lot of ensemble music. The site is mostly in English.