Where can I find Web based information about Federal income taxes paid
by various household income groupings. For example: 5% of all
households (or taxpayers) pay 22% of all fed income taxes.

Hello Vincent -
I think the Cato Institute, the leading libertarian think tank,
answers your question, although you may have to do some simple
arithmetic to get the percentages.  At their "Fiscal Facts and
Figures" site,   http://www.cato.org/fiscal/2002/factsfigs.html , take
a look at two tables:  "Share of Households Paying Federal Income Tax
by Income Group, 2001," and "Share of Federal Taxes Paid by Income
Group, 2001 (Includes Individual Income, Payroll, and Excise Taxes)
Between the two, you get the number of returns in each group, the
total returns (so you could figure out that people in a certain income
bracket represent what percentage of total filers) and what share of
the total income tax burden each group bears.  Note, however, that
other taxes besides income are included in the "Share of Federal
Taxes" table, such as payroll (like Social Security and Medicare).
The site also gives you stats on how much the top 1% earners in the
country pay.

You might also want to download the preliminary version Congressional
Budget Office report, Historical Effective Tax Rates 1979-1997
available at: ftp://ftp.cbo.gov/28xx/doc2838/HistoricalTaxRates.pdf . 
This was released just last year, but the data stops, as the title
indicates, in 1997.  It has tons of tables and some textual
explanations like:
"Households in the highest income quintile paid 65% of the four
largest Federal taxes in 1997, up from 57% 18 years earlier." (p. xv,
xvi).  Table G1-B looks especially useful, if you can live with the
age of the data.
Does this answer your question?