Yes, but it is usually very slow; standard is 9,600 mbits/sec unless you're going WAP.
If both your laptop and mobile have IR, then it is very straightforward. The mobile acts as the modem and there are no additional costs.
Better but much more expensive in hardware is to have a cable connection (£70) between mobile and the PC card Modem (£70-100). You have to have a Modem and Phone that support each other. PSion and Motorola go together.
I've used both methods. The IR was sufficiently unreliable to make me spend the extra on the cable.
Okay for e-mails but too slow for browsing.