Anyone know why certain routers get hot and others don't. I've recently come across a Dlink and linksys that you could cook on even the computers are off, and a netgear that is as cool as a cucumber even when screaming data through.

Strange.
=============
Try zyxel's they usually overheat and drop dead.

On the other hand our draytek in the office doesn't get to hot.

If your downloading constantly at high speeds your router will get hot if it has a decent CLI see if it shows cpu usage.

Always try and keep routers in the open not with stuff stacked on top etc
=============
It depends on the design quite simply. Cheaper routers will not have as good airflow, or heatsinks on the CPU etc. Netgear make very nice routers but you do pay a premium for that.

I usually always supply Netgear as I get no complaints from clients with them, although Linksys I do also supply. The only brands I avoid are Belkin (nothing but trouble) and unknown OEM brands.
=============
I quite like Billion. They seem to run nice and cool. Some processors and chipset do run hotter than others so you will find differences. Sometimes its just down to design and airflow - some are designed to run hotter than others. Doesn't necessarily mean that anything is wrong.
=============
I'd never really paid much attention to it, but the difference in heat output from the D-Link, Linksys and Netgear was astonishing.
=============
Funnely enough my BT voyager Router which I have at work has started cutting out my connection and after a bit of digging on google I found this was because of overheating. So I am going to modify it's cooling !
=============