How To Make Free VoIP Calls

It's not suprising that a lot of readers of this blog ask, via the comments, how they can make a free VoIP call from a specific country to another, where the callee has a phone but no computer. So I thought it'd be worthwhile giving a summary of some of the services that have come out this year, in terms of categories rather than specific software.
First, let me answer the question(s) as simply as possible. There are some countries that are less likely to have free calling between PC and PSTN/ mobile phones - not that I've seen. Two of those countries are India and China. Maybe it's because they're the two most populous countries in the world, and few companies want to give up the potential market share.
The only exception I've run across is Jajah (see below), which is currently offering free landline and mobile calling to/from China. But if you run their trial, you can also make a 5 minute call to/from India as well. If I find any other VoIP services that allow free landline calls to/from India or China, I'll write about it on this site.
On the other hand, if both the caller and callee have a computer with a non-dialup Internet connection, you can make all the free VoIP calls you want, between any two countries, with pretty much any softVoIP client. For example, Skype, Google Talk, MSN Live Messenger, Yahoo! Messenger, Gizmo Project, etc.
If you want to call or receive calls on a regular phone via a VoIP network, there are SIP-based adapters (hardware). You'll still need a broadband Internet connection, but won't need a computer. But how many people have a broadband connection and no computer? Not many, I'm guessing.
For many countries, there are a few options for free PC-to-PSTN (PC to Phone) calls, occasionally including mobile. Some are time-limited promos, some are permanent offers. Here are just a couple of options. (I'll not cover everything here.)
(1) Skype just finished a July promo for free PC to Phone calls from Canada and the US to Mexico, Japan, and the UK. I'm guessing they'll have other country offers later this year. They also have free PC to Phone calls within Canada and the US until Dec 31/06. But if you don't live in either Canada or the US, you'll need to pay for their inexpensive SkypeOut service, which lets you call PC to Phone to many countries.
(2) Gizmo Project has a permanent offer that let's you call PC to Phone between 60 countries (but not India and China). However, both caller and callee need to register as Gizmo Project users. (This might mean having to download and install the software as well. So if you don't have a computer, you may have to ask a friend. Keep in mind that you are allowed up to, I believe, three phone numbers per registrant, so your friend may not want to help you :)
(3) Jajah allows PC to Phone calls free for up 30 minutes. It's unclear exactly which countries are allowed and which are not, as I've read different things. They do have a 5-minute trial call, and their list of countries includes India and China. But when I read their web pages, I see only China included in the 30-minute free calls, between registered users. You should note that Jajah allows you to make Phone to Phone calls, not PC to Phone calls.
This is just a sampling of some of the nice VoIP plans currently available. If you know of others, please feel free to mention them in the comments section. I will try to put together a comprehensive free-VoIP guide, before Christmas time, that points to articles both here and on other websites.