Remote Access

Our Network runs on NT 4.0 with most users running under Win98. I am going to be setting up VPN for our employees. Basically for getting e-mail and being able to retreive files stored on the network drives. I would like them to be able to log in from anywhere without any kind of security call back. Our office has 100 employees and must support 20-30 users via the VPN. What is the best out there???