Ideas for integrating a SIP account, N900, Magic Jack, Linux, etc...

[Linuxguy123]

I'm looking for some ideas on overhauling/revamping our telephone
system.

We are two busy working professionals.  We spend half our weekends away
from home.   My wife still has an iPhone.  I'm getting an N900.   We
have a landline with (terrible) voice mail service.

I want to tie it all together, somehow.  

I'd like to get a VOIP account somewhere and connect to it with a SIP
server of some sort so that I can do things with that connection. 

I'd like all our voicemails to be stored on that SIP server, so we don't
have to erase them, etc.  Actually, I'd like to get them as emails that
we can listen to and organize.   

I'd like to be able to call into my SIP server with the N900 and maybe
the iPhone and then make (cheap) calls anywhere.

Can one share a Magic Jack connection as a SIP service ?

How can I use Linux to do some of this stuff without resort to a full
blown asterisk installation ?

Thanks !