Is there any baryonic matter in inter-galactic space? and if so, what?

Answer 1

In addition to being very low density it is mostly ionized. We learn a lot about cosmology and (galaxy) clusters through studies of the intergalatic medium. If you want to learn more, search for IGM or Intergalactic Medium.

Here is a wiki article about it to start you, but I am dubious of the interpretation there that half of the baryonic mass of the Universe is in the warm-hot or hot IGM. I need to see the journal article(s) that make that case before drawing any firm opinion though.

http://en.wikipedia.org/wiki/Intergalactic_medium

Answer 2

Sure. Mostly hydrogen, some helium, and a smattering of other elements left over from supernova explosions. Of course, the overall density is very low.