Most secure way to buy bitcoins would be
MTGOX.com or
BTC-E.COM.
But considering the hype around bitcoin here it could take up to a month untill you got your BTC.
Literally the best and fastest way is knowing someone you trust, and then you can buy BTC off of him.
A transaction like that can be done in 30 minutes including waiting for confirmations for your transaction ID.
Back in my topic I explained how I started btw =P, maybe you'll find that interesting.
It is more about trading.
Cheers,
Nexigen.