VPN
VPN capabilities are limited to pass through mode for PPTP and IPsec clients. Port forwarding to one PPTP and IPsec server is also supported, provided you enter the proper ports.
Logging and Other Features
The WRT54G's logging features are the usual Inbound and Outbound traffic logs that you've come to expect with Linksys routers. But once again, there's work left to do since the usual SNMP Trap logging mechanism that's used to send detailed logs to a LAN server isn't implemented yet. You won't be able to save logs to a file either, but you can clear them.
Other features worth mentioning are the ability to disable the Internet Sharing function and use the WRT54G as a non-NAT router. When in this mode, you also get to control the interfaces (but not the direction) that Dynamic Routing RIP-1 and 2 messages are allowed on. You can also define up to 20 Static Routes in either Gateway or Router modes.
Version 1.01.4 firmware added a built-in client for TZO's Dynamic DNS service, in addition to the usual dyndns.org offering that you find on most routers that implement dynamic DNS. I may be biased, since TZO both hosts SmallNetBuilder and provides our DNS, but if you're going to use dynamic DNS, you really should use a reliable service, which is one of TZO's strengths.
That about wraps up the features. Let's move on to Performance.