How can I connect a remote laptop/pda to a company network via VPN?

I'm trying to set up a VPN to connect the networks of multiple office buildings. I'm using Cisco equipment so setting up the VPN for the offices is easy but I'm not sure how to enable mobile users to remotely connect to our network via VPN. Is there any special hardware or software I need to purchase/download?|||they either need an account on the vpn endpoint (firewall or router) or in your domain, if it's the domain account you need to set up your vpn endpoint to use radius to authinticate. then you'll need to make sure the laptops/pda's have the cisco vpn client on them (free DL from cisco if you have a CCO account with them) unless your using the "easy web vpn" in which case on the vpn client you just need them to hit the website that your vpn endpoint hosts.