How can I converge all my phone lines for easy access?

I have a regular land line, 2 voip lines,and a cell phone. Is there some way I can make all of the available throughout the house? I can buy a new router, switch voip company's and/or buy new phones (except for the cell). I was thinking something like an office system, but definately focused at the home user.

The landline is only used as a backup dialup connection and the occasional fax (send/receive), but I would like to have easy access to it in case of an emergency.

The landline has no extra features. The 2 voip lines, and cell phone all have caller id, call waiting, voice mail and 3 way calling. I would like the ability to conferece between them, and direct a fax received on any of the lines (except the cell).

I also have 3 pc's in the house that all run windows xp home, but only one of them's on all the time, if there's a virtual solution.

If I'm asking too much, or it would cost a lot, what about something that comes close. Thanks! :)

Check Staples, Best Buy etc. There are several products on the market (in the under $50 range) just for that purpose. Remember, your land line phones are all daisy-chained, so all you need is one line to any phone jack to your computer via said device and all the phones become available to be answered on your computer or on a nearby land phone. The advantage is it lets you make LD calls from any house phone via voip so as not to pay the phone monopoly their outrages rates.

you need to get a pabx: private automatic branch exchange.
that will let you use all the phone lines from all the phones.
if you only had two lines, you can get the uniden cordless phone that has two lines, so all phones in the house will have access to both lines and you can do intercom between handsets.
The pabx will be expensive and may require some rewiring.
Also you will have to dial 9 before getting an outside line!