Parallel ISP's?
 

Have a home network - five computers, two printers a wi-fi transmitter, a VOIP adaptor and an LCD TV (which, believe it or not, has its own e-mail address).

It's currently fed by a cable internet service (6 mb down, 1mb up) which starts with a co-ax end that is screwed into a modem/router.

For all sorts of irrelevant reasons I'm considering having a second internet supply, through a "copper pair" telephone cable - at a miserly 1.5mb down, 256k up.

Is there any funky way of connecting these two together - or would I have to decide which machines would go onto which service....and would they still network with each other?

There are hardware and software solutions. Check out things like Vyatta and Mikrotik. Search terms like "WAN load balancing" and "dual WAN router" should point you the right way. D-Link used to have something. I use this technique (but not this hardware) for my aggregated 160Mbps symmetric feed.

How about putting a second network card in a machine and using that machine as the gateway between the two. I was doing that 20 years ago between ethernet, token ring and appletalk. Of course I was using a real O.S!