Definately check out Stan Hugill's recordings. The recording of "Shanties from the Seven Seas" that Chanteyranger mentioned is available from CAMSCO, at least that's where I think I got my copy from. You can get pretty much anything from CAMSCO, including my CD - the only reason I only mentioned the CDBABY website is that they have my CD set up to play samples. The Chanteycabin site mentioned earlier is excellent but can be expensive for those of us in the States.

I would also recommend any recordings by the English group "Stormalong John" - this is the band that Stan Hugill used as his backup group for a while when he was touring. And, as requested by the original poster in this thread, all of their recordings are a cappella, with the exception of the odd song here and there. I'd also second a thumbs up for the Holdstock and MacLeod recordings. Also recordings by "The Keelers."