Well, hacking someone's website and hacking their personal computer are two different things. Most of us who have websites use a hosting provider - and thus our stuff is stored on their servers. Those computers are out of our control - and it's up to our hosting providers to keep those from being hacked.
Hacking someone's PC is different. And in general, these days, it's not done through brute force attacks (ie password cracking). It's done via viruses and spyware. Both of which are capable of collecting information like passwords, bank websites visited - everything and anything - and reporting it back to the virus/spyware creator.
Therefore, the best way to protect yourself is to keep your computer free and clear of all viruses and spyware - which means using the most secure software you can, keeping it updated, and running regular virus and spyware checks. I'd also recommend a hardware and/or software firewall - both if you're really paranoid. And if your computer has been infected with something particularly nasty - rather than risk reinfection or residual effects - reformat the drive and begin fresh.
As far as keeping your website safe - don't hand out your password and use a good hosting provider

I'm sure I'm forgetting plenty of stuff, but this should be a good place to start.