line break in sed

[Ben Luey <lueyb@gridley.ACNS.Carleton.edu>]

I've a long one line text file formated like:

name1, name2, name3, ....... name9999

I want to format it like:

name1
name2
name3
....
name9999


I was thinking of doing:

sed \s\, \linebreak\g

But I don't know how to insert a line break -- I've tried \n, but no luck.
The name page talks aobut /<newline> but that was treated as text. 


Thanks,

Ben