Well I've never actually had VOIP service but am defiantely interested in it. I have looked the the options and here are a few things I've found that I can compare. Feel free to add anything you wish. These are all for unlimited minute residential services.

Monthly Charge:
Vonage - $24.99
AT&T Callvantage - $29.99
Lingo - $19.95
Packet8 - $19.95

Activation Fee:
Vonage - $29.99
AT&T Callvantage - $49.99
Lingo - $29.95
Packet8 - $60.00

Rebates:
Vonage - $60.00
AT&T Callvantage - $60.00
Lingo - ? (Didn't see any but they seem to be the only service to provide the phone adapter for free)
Packet8 - $60.00

Free Months of Service:
Vonage - 0
AT&T Callvantage - 1
Lingo - 1
Packet8 - 2

Total Upfront Cost:
Vonage - $54.99 + tax
AT&T Callvantage - $0
Lingo - $29.95 + tax
Packet8 - $0
**All prices are calculated after rebates, upfront costs may vary**

Voicemail:
Vonage - Phone , Online, E-mail
AT&T Callvantage - Phone , Online, E-mail
Lingo - Phone , Online, E-mail
Packet8 - ? (Couldn't find info on services on website)

Other Services Offered:
Vonage - 11
AT&T Callvantage - 12
Lingo - 13
Packet8 - 5
**Listed at end**

I decided to add a poll for this guide for others to tell what they use or prefer. If my information is incorrect please correct me so I can fix it in the guide. Also please add comments to this so those of us interested but don't have the service can have some incite on what to expect. Thanks.

Here are some other services provided by the companies:

Vonage:
Voicemail
Caller ID
Call Waiting
Call Forwarding
3-way Calling
Call Transfer
Click-2-Call
Call Return
Caller ID Block
Repeat Dialing
Ring Lists
Call Hunt

AT&T Callvantage:
Voicemail
Caller ID
Call Waiting
Call Forwarding
3-Way Calling
Conference Calling
Call Log
Phone Book
Locate Me
Speed Dial
Do Not Disturb
Emergency 911 Dialing
Safe Forward Number

Lingo:
Voicemail
Caller ID
Call Waiting
Call Forwarding
3-Way Calling
Anonymous Call Rejection (ACR)
Caller ID Block
*69
Do Not Disturb
Emergency Calling Service
Redial
Speed Dial
Refer-A-Friend ($25 credit)
Money Back Guarantee

Packet8:
Voicemail
Caller ID
Call Waiting
Call Forwarding
3-Way Calling
Caller ID Blocking

Websites:
Vonage
AT&T Callvantage?
Lingo
Packet8

From the looks of what I have found I'm going to be getting Lingo, if anyone has an account I'll get them the $25 referal.

hi dude
well, maybe I'm wrong but I vote in other because I use Skype so I'm not sure if correct or not what I don't understand is all info above is need to pay for use and for use skype is free??? I'm wrong??

well that's not really the same type of service since you can't use a regular phone with it and it's not free to call people who don't use skype.

I have used vonage for about 7 months now and like it a lot. The only problem I have had is it looses caller id once in awhile. A simple modem off then back on fixes it.
We had to go to it because our local phone monopoly charges per phone call, 5cents per min after I think 5 or 10 mins. The usual bill would be around $60 or so. If you had dial up, like my sister, the bill would easliy go over $100 each month. The guy that installed her phone told her it would be cheaper to get cable...lol..

ive been using vonage for a year now, its awesome how they kept lowering their price to 24.99. i use it as my backup phone (to cell phone) and to make lengthy long distance phone calls. fav feature on there is call xfer, where i can transfer someone im talking to, to another phone.

hey, I have a Lingo account, I think I had referred you to it in another forum? Anyway, I would love the $25 referral credit...oh, and trust me, you will love their service! Let me know!

i myself am waiting for Shaw to start their voip service, what i like about it is they put a seperate modem in a box outside your house and hook it up so you can use the phone outlets that are curently in your house instead. and they also have a special band for the voip modems so u get much better quality and it doesnt interfer with ur speed

I just cancelled my vonage account, but that isn't due to their service, it was how my house phone lines were configured.

I need to rewire my house phone wires before I will reorder from vonage again. Their $14.99 a month is good for my household since we barely make any phone calls.

The only thing I hate about vonage is that they send you a linksys digital phone adapter, which is also a router. So I have to congure the damn linksys not to act as a dhcp server, connect it to my netgear, then to my home network. It was annoying to have two routers.