There are hundreds of providers worldwide, which one or ones you use will depend of the feature set you want. I have tried out a few and will give you my opinion on them, armed with a little information you can select the one that suits your situation.

In most cases if you are calling someone who is using the same service provider then the call is treated as an internal call and will be free no mater where the two of you may be in the world.

Skype (www.skype.com)
When most people talk about VoIP they will normally have at least heard of Skype, while not the first to provide the service they have definatly raised the profile of VoIP in the public eye. Initially based on Peer to Peer service Skype built a large following of loyal users, they provide a free service using thier own propriatory software which you can download from their website.

If you only wish to make calls to other Skype users then it will cost you nothing to join and no ongoing costs. If you wish to make calls to the PSTN network then you will have to prepay for Skypeout credits, the call rate is approx 2c Minute to most countries.

Skype also includes an instant messanger as part of the software, the newest version also includes the ability to use a web camera so see the person you are talking to.

Engin (www.engin.com.au)
While I have not personally used this provider they are making a concerted push in the Australian market, aimed particularly at the home market as a simple to use service. Engin provide users with a preconfigured ATA (Analogue Telephone Adapter) they have dubbed the VoiceBox, you simply purchase this from a retail store (Dick Smith, Tandys etc..) take it home and plug a cable from your broadband connection in one socket, your phone line in the other and your cordless phone in the other side.

Then you call the activation number and quote them the code from the kit and specify what account type you would like based on their available plans, sound simple doesn’t it. Well things don’t always go smoothly, occasionally it takes a little back and forth to get things up and running but overall it works. Costs are a little higher than some of the other providers for the monthly plans but for a simple service if you make a lot of STD calls to friends and family then it can save you a bundle. Rates are 10c untimed to any Australian landline, international rates 3.5c a minute to most countries and engin to engin calls are free. The plan also includes 1 local phone number so that people on the normal PSTN network can call you.

Freshtel (www.freshtel.net)
Freshtel were one of the first providers that I used, like Skpe they provide their own software (Firefly) free of charge, they have also introduced their own ATA but you can use any of the available ATA’s and Softphones with their service. Call quality has always been very good, Rates to capital cities are 10c untimed if you prepay on a plan otherwise it’s 6.9c minute, their rates are higher for international calls as well at 4.9c minute.

Oztell (www.oztell.com)
This is who I use for most of my VoIP requirements, their website needs work mainly because they provide a lot of information which can be daunting for a novice. Unlike most providers who started with Peer to Peer communications and then developed a call termination side much later Oztell built them together. Initially their focus was business as an addon for PABX’s but they are now realising the potential of the retail market and have shifted their focus somewhat.

For me the primary requirement was not only for outgoing but for incoming calls as well, in this Oztell covered all the bases. For connection you can use their softphone or any of the available ones from other suppliers (I use the X-Pro from Xten) or any ATA, as part of the standard service you have the ability to make outgoing calls using VoIP for a small monthly fee ($1.95) plus call costs. On the cheapest rate thats 9.9c untimed to any landline in Australia, international calls are approx 2.5c Minute. Its when you add the additional features they really stand out, on the integrated phone service ($6.95 month) you also get two local phone numbers one of which can be set up to recieve faxes which will be converted to pdf and emailed to an email address of your choice. You also get the use of the web pabx which can route your calls to multiple numbers, set up an answering service or give the user the ability to redirect the call to different numbers ie. press 1 for sales, 2 for support etc.

You can also get additional numbers in other cities in Australia and terminate them on the save service allowing others to call you for the cost of a local call. Additional number are only $1.95 per month, most of the other providers charge $5 – $10 month.

Pennytel (www.pennytel.com)
Pennytel started out with phone cards and buying large blocks of call time from various providers to give their customers cheap rates, they have jumped on the VoIP bandwagon and have had their ups and downs. Overall they are still very good and have ironed out most of the problems with their network, connection is using one of the freely available soft phones or any of the standard ATA’s.

Call quality is good and in some cases very good, I manly use them for international calls as their rate is approx 1.5c minute I also use then for short calls in Australia as well as it is the same rate. Calls to mobiles are also great at 19.5c minute. If you make alot of outgoing calls you can also purchase blocks of time at a cheaper rate and the now also have an untimed plan where you pay a monthly fee and get untimed calls for 9c to Australia New Zealed and Signapore.

Still no incoming numbers but they do have shared access numbers where you can have someone ring a local number (1300 in Australia) then enter your pennytel number to call you. Calls between Pennytel users are free.

Faktortel (www.faktortel.com.au)
Again a provider that I have not used but they came a very close second for me behind Oztell. Connection is via softphone or ATA, they can even provide you with one pre-configured for their system, call quality is good but you will need to prepay. Their plans are cheaper than Engin and overall quality of service is better, rates are 10c untimed to any landline in Australia and approx 6c a minute for international calls, they can also provide you with an incoming number on any plan and calls between users are free.

Well that wraps up the reviews, there are many other providers out there one good source to check out how others feel about the different providers (Australian at least) is over at Whirlpool . I hope this has shed some light on the subject for you.