Audio Damage set all their older plugins to free downloadable. Lots of great stuff amongst these, Dub Delay recommended.
Get Decent Sampler for free and download tons of sounds for it at PianoBook , also free.
Convert MP3 format to MIDI format on this site.
An exploration of the sounds and rhythms found in electro-magnetic fields from MakeNoise. You can find free samples of recordings like these and more from them on their FreeSound page.
Nice vinyl mix of Rare Grooves to chill to from Mindpray.
Bosca Ceoil is a free tool for making Chiptunes music.
If you should have missed this, here are free samples from Jamie Lidell for you on his Bandcamp.