I found a link to
http://scry.wanfear.com/~greear/vlan.html on tldp.org, that should get you started.
Basically
support can be patched into the Linux Kernel for VLANs so it's a matter of seeing if it's in your kernel already and adding it if needed and then finding the userspace utilities to configure it. The concepts will be a lot easier to get if you have worked with VLANs on switches/routers before.
The only non-propriatary VLAN tagging standard I know of is 802.1q, so this will have to be supported and turned on on the network port that eth0 is plugged into as well.
Edit - support is not built in, but can be patched in. That and we don't have a vbCode for strikethrough?