Well, if you're a developer, presumably this isn't the first computer you have owned. I'm using a 5 year old cheapy HP laptop as my dev server and it works wonderfully.
There are other alternatives, of course, Cloud9 premium account gives you full shell access, Action.IO gives you full shell access as well.
Regarding the idea of using an old laptop as a dev server, have you run into any issues as a result of having the laptop on all the time (such as overheating)?
Also, how would you set it up so that you can log in to your laptop from outside your LAN? I have a few old machines lying around and it would be great if I could put them to use as servers.
Shouldn't have overheating issues as long as you sit it so that the vents can breath. I leave mine in the basement where it's a little bit cooler. My current uptime is 45 days, I only restart for kernel upgrades and never shut it down.
I purchased dynamic DNS, which IIRC is around $35/year, well worth it for the convenience of logging into my home server whereever I am.
There are other alternatives, of course, Cloud9 premium account gives you full shell access, Action.IO gives you full shell access as well.