SACD & DSD Questions

A friend of mine has a fairly new PS3. From what I've read on the FAQ at the current PS3's are not capable of SACD, but are compatible with DSD disks. His Integra 40.2 receiver is also DSD compatible.

What I don't understand is exactly what DSD (direct stream digital) means in relation to SACD or any other formats.

My SACD player outputs a stereo analog signal via RCA. I'm assuming that some SACD player can output via PCM on HDMI cables?

I guess I don't understand where DSD fits in.
DSD comes in a few flavors, one of which is what is taken off an SACD disc. There are a few players, such as the Sony XA5400ES and some PS3s, that will play non-SACD DSD. Korg makes a player-recorder.

Many SACD players will output PCM and/or DSD on HDMI.

What are some other examples of DSD formats? I guess I thought that DSD was essentially the same as, or developed for, SACD.
I read that link already and just read it again looking for what I missed. I see there are several DSD mastering formats, but other than SACD I don't see any other DSD formats that the average person can purchase. It just seems odd that PS3 would drop SACD but keep DSD when there isn't anything on the market to play.

Is there a link with blu-ray and DSD?