LocalBitcoins - is a marketplace for trading bitcoins locally to cash or online payments of your choice. - Accepts US residents!!!
CoinBase - probably the biggest bitcoin wallet website where you can buy bitcoins using your bank account (free 1$ worth of bitcoin after verifying your account!!!).
VirWox - probably the only way to buy Bitcoins with Paypal. You would have to buy Linden$ and then convert them to Bitcoins.
1wbe - exchange that has very high liquidity and great for beginners
CoinMama - offers Bitcoin buyers with an easy, fast & secure way of purchasing Bitcoins (use 744XX276 coupon code to save!). - Does NOT accept US residents!!!
igot - Australian based Bitcoin exchange, has very user friendly interface.