Sorry .. forget to add this..
Unless you have a L3 switch which will route internally between Vlans, for every Vlan you have configured on th eswitch you will need a separate router interface.
Although its possible to multi-net an single interface (that is apply more than one IP address to an interface) if you are connecting to a Vlan switch then you need separate connections from the router to the switch as broadcasts from one vlan only remain in that Vlan therefore you need a router to route between them.
Therfore depending on how many Vlans you have and how many users on that Vlan, you may want to consider buying a l3 switch to act as a gateway, something like the passport 8003, this way you avoid the latency of traffic passing from a switch to a normal router and then back out to a switch again. Also you can utilse functions such as Multi-link trunking and Vlan tagging.