I'm trying to enable telnet access remotely to my router, a Linksys WRT54G v8.0 but it doesn't seem to work. I can access it from my home computer via telnet but not from another computer outside my network.

I haven't tried this myself, and, I use tomato firmware on our WRT54GL's, not the stock firmware, but I suspect that for this to work correctly, you may have to setup a port forward for telnet to the internal (LAN) IP of the router. I know this doesn't make much sense but it strikes me as something to try if it's not working on it's own after you tell it to allow remote management access via telnet.

I just tried it, it doesn't work.

Then maybe they're not supposed to. I just looked at a WRT54GL running Tomato and the remote access page shows you can remote access via http and ssh and can even designate allowed IP's. But there's nothing for remote telnet access. I suspect it's not actually supported. Any reason not to use http? I know the ssh/telnet interface on these 54GL's is nothing to write home about and I doubt you could make changes in it's config from either ssh or telnet so you'd likely be better off using http anyhow.

I'm lazy and I want to have shell access to my router, to wake on lan, you know, geek stuff ...

Then use ssh and not telnet............that's what I'd do. If your router isn't capable of remote ssh, then upgrade the firmware to tomato and you'll be able to.

I looked up Tomato and it's not compatible with V8 lol. My WRT54G that is. It's too big, only have 2MB of flash.