Bogleheads is a great resource. Be prepared though, if you want to ask a question in the forums you need to do your homework first. They will want to know about any current investments, income, debts, risk tolerance etc.
A simple 3-fund portfolio may work for you, giving you exposure not only to the U.S. stock market but to the international stock market and the bond market:
Vanguard Total Stock Market Index Fund (VTSMX)
Vanguard Total International Stock Index Fund (VGTSX)
Vanguard Total Bond Market Fund (VBMFX)
The percentage that you have invested in each would depend on your age, risk tolerance, and your asset allocation in any other investments. For a young person without many other investments you might do 50% U.S. stock, 20% international stock and 30% bonds. Then add to it regularly.
http://www.bogleheads.org/wiki/Three-fund_portfolio