Hey Darrin,
Very nice web site.  Keep it alive.  There clearly are not enough
Woodstock sites on the web, which surprises me because there certainly
seems to be plenty of interest in Woodstock here and around the world. 
I have heard that there is a group of people in Australia (I think) who
actually consider Woodstock to have been a monumental event of cosmic
significance.
I don't know where you got your info on the actual schedule of
performances, but the info I have shows a somewhat different order of
performers.  My schedule comes from the 1969 publication "Woodstock - A
Special Report by the Editors of Rolling Stone" and a list compiled by a
friend who was present, is somewhat compulsive, and wrote his list while
he was there.  He is certain his list is accurate.
Here it is.  
Friday:  
Richie (of course) at 5:07
Swami (remember, from the movie, it was still light out when he spoke)
Sweetwater
Bert Sommer
Ravi  
Tim Hardin (my friend and Rolling Stone disagree on this one.  RS thinks
that Tim went on before Ravi and my friend's list shows the opposite)
Melanie (this was originally ISB's spot but they freaked out and would
not go on.  too bad for them.  Melanie prospered with a memorable
performance and they disappeared)
Arlo
Joan 

Saturday:
ISB  (here is an interesting one.  According to ISB's own web site, they
played on Saturday, after refusing to go on Friday night.  Thay much
seems certain.  But their manager remembers them playing between Canned
Heat and the Dead.  Can't be true, though, because pictures show that
ISB played before dark and Canned Heat played into the night and the
Dead did not follow Heat.  Also, RS puts Quill in this slot, but I think
they got it wrong also.  Maybe they did not know the difference, since
both bands - Quill and ISB were not well known at the time.  Anyway, I
am going with my friend's list that shows ISB leading off on Saturday
afternoon.)
Sebastian (this one is pretty certain.  They were stuck for performers
today, because of the traffic and recruited Sebastian and Country Joe)
Country Joe (alone)
Canned Heat
CCR (RS thinks that CCR followed the Dead.  Who knows?)
Keef Hartley
Quill
Santana 
Dead (my personal favorite band, and although they claim this was their
worst performance ever, tapes of it do not bear that out.  It was weak
but not all that bad and the stoned rap between Phil and one of the
pranksters in the middle is pretty funny.)
Mountain
Sly (RS reports that Janis followed Sly.  My friend disagrees.  You be
the judge.)
Janis
Who (great show.  I actually remember this one, nearly 28 years later.)
Airplane (the morning maniacs, who woke us up after napping for just a
few minutes after the Who closed)

Sunday:
Cocker
(rain)
CJ and Fish
10 Years After  (Alvin Lee can thank his lucky star that the movie was
made, because it clearly kept his career alive longer than it otherwise
would have lived.
the Band
Winter
BS&T
CSN&Y
Paul Butterfield
ShaNaNa (the luckiest 30 minutes of their lives, and they readily agree)
Jimi (of course)

Finally, you asked about Jeff Beck.  Although he was scheduled, he never
showed.  I don't know off hand why not.  I don't think it was an Iron
Butterfly thing (couldn't physically get to the site from NYC).  I think
he just bagged it, and surely regretted it.

I collect original Woodstock memorabilia.  I have loads of books and
mags, etc.  If you know of anyone else who collects, I would love to
correspond with them.  If you know of any good sources for stuff, please
let me know.
You can email me back at this address, but the one I would prefer to use
is my AOL address --  MaxYasgur@aol.com.  I am just trying out this IBM
ISP for a month for free and will probably drop it soon, but I will
retain the AOL address for a while.
Peace,
Mark