Is there anyway to do this.

I have both a Windows and a Linux box sitting here. I want to be able to dail into one of those boxes and use the internet on my laptop somewhere else from the connection i have at home. Is this crazy or do people do this?

I've done this.

When I had flat rate ISDN at my parents house, I used a dial in from my house (at 5p per call, unlimited time) to get flat rate Inet access whilst waiting for ADSL to be installed (which took around 4 months...)

There is a howto somewhere that explains how to setup dial in under Linux.