Where can I get a list of president Bush's stock holdings (both the
name of the stock as well as the number of shares), his wife's
stock holdings, vice president Dick Cheney's and Cheney's wife's
holdings as well as Rumsfeld and his wife?  If possible can I get this
information about George Bush senior and Barbara Bush?

You can find Bush’s 2001 tax return at the taxhistory.org site.  Go to
Schedule B (of Form 1040) for a list of sources for dividend income. 
Note that the following sources of dividend income are “pass-through”
entities such as trusts.  These entities own stocks (or other
investments) that earn dividend income. The detail of the stock
ownership is not reported separately in GWB’s tax return.  This site
also includes Cheney’s tax return.

http://www.taxhistory.org/Presidential/default.htm

THE LONE STAR TRUST
GWB RANGERS. CORP. [Bush owns 100%]
NORTHERN TRUSTS CO. AS TRUSTEE
HENRY G. FREEMAN JR TRUST

The opensecrets.org site includes GWB’s “Public Financial Disclosure
Report” for 1999.  There was a requirement to file this report when he
was a governor.  This report includes 24 pages of GWB’s stock holdings
and other investments.  It appears that the detail stock holdings of
most of the above trusts is provided in this report.

http://www.opensecrets.org/pfds/index/P00003335.htm

The findlaw.com site includes GWB’s “Public Financial Disclosure
Report”.   (Sorry, I couldn’t load it so I don’t know what year it
relates to.)  This site also includes the reports for Cheney and
Rumsfeld.

http://news.corporate.findlaw.com/legalnews/documents/archive_b.html

http://news.corporate.findlaw.com/hdocs/docs/gwbush/gwbush-sf278.pdf

The following articles discusses Bush's investments:

http://abcnews.go.com/sections/business/TheStreet/bush_makeover001025.html

search “George W. Bush” “Financial Statement”
“George W. Bush” “Financial Disclosure”