The Edirols take anything from a 64MB Compact Flash card up to a 2GB card. The 64MB is the basic card that comes with the recorder.
In the first true "field test" of my Edirol R-1 at a recent filk convention in Canada, I used two 512MB cards and recorded to MP3 at a 128 kbps rate. Managed to get almost 18 hours total of music, much of it (especially stuff performed on stage with PA) at fairly decent quality.