Simple tutorial on setting up a PBX?

I've had to set up phone systems for a small agency two or three times. My best experience has been to identify a local telecommunications company and let them guide me as to systems and equipment... You might want to call around, you may find that the best solution will be offered by an expert in the field.

I haven't tried it, but there's also http://www.asterisknow.org/ which looks a little less ugly than TrixBox's free version. I can't really answer anything else, as I haven't yet set up an Asterisk machine of my own.

I've set up an Asterisk@Home system for a business (I think it's called AsteriskNow these days) and it worked *great* ... you can use either regular analog phones with an adapter, or you can use SIP phones -- either handset, or if you don't care about having a handset, you can use a headset like me. We were literally up and running in a few hours after I finished the configuration.

Asterisk. My recommendation is to learn the backend config files by hand. Just to understand how it works - then by all means use a GUI. You will be glad you did. Also trixbox is a convoluted POS. FreePBX is bloated as well. My vote is to spend a bit of money on www.thirdlane.com if you want to use a GUI. It's a lot nicer and still inexpensive compared to a traditional PBX system.

Also, know that two lines will likely not be enough for 5-7 people. Two lines means one person gets to talk on the phone while a fax is being sent, or two people can call out while nobody can call in, and so on. You may want to do a little "walk around" research during the day in the office to see how many simultaneous calls you have to account for.

I would think asterix would be overkill. You still need to pay for the hardware if you want handsets etc. I would suggest ebay for a small used analog system. There are a lot around as corporate users replace small office systems with VoIP stuff. I would add a third extension too. If it is a green field set up (i.e. he doesn't need to keep an existing number) you might want to see what the voice over IP operators can offer. They may well be able to deliver all the services you need cheaper. Here I would look at Engin, but I suppose you might try Vonage? If this is more than you want to do, the local independent IT guys often do small PABX setups.