I actually was thinking of writing a hub about this when I wrote a hub on Self Hosted Message Boards. There are people who do not have the time to do the whole backend thing from the server side to run their own board and some people just want a free board. When it comes to these, there are pros and cons when it comes to going with these free type of boards. One of the biggest cons I can say is that there are usually some sort of limitation if its is not for space, they have also addvertisements on the boards too.

Proboard is a board is a board that I have only been a member on.  I don't like them that well though, but some people may like it.  The whole idea is that you can run a community on this.

freeforums is another site that looks to host free boards. If you like Phpbb 3, this is what they host for you. I have never tested out their service, so I really do not know how good thier service is.

Forumotion seems to host a few different types of forums out there. Here is the list:

• Invision - It is probably1.3 as this is the only free version.
• Phpbb 2 and 3 - There seems to be a option which phpbb that can be chosen.
• punbb

I have not tried this site, but if you are interested, I would check it out.

Forumer is another site that offers free forum hosting. You also have some board choices here.They include:

• Invision
• Phpbb 2 and 3

The same thing goes for invision as it is probably 1.3 because of the fact that anything 2.0 and up is not free.

Prophpbb is another site to check out that is using Phpbb 3.

Invision Plus Is another forum out there that is using invision 1.3.

Invision Free is another one that is using Invision 1.3. When I had found Invision many years ago, I found this one until I finally broke down and got my first domain name website that I paid for.

Zetaboard is another board that is not based on phpbb and invision, but Zetaboard is from the people whom run invisionfree.

SMF for free is another forum one that is out there that is free. I have tested this out for a little bit. It's decent.

The pros are not having to deal with maintaining it on the server side of things.  The downside is that you don't have the control of things and in most cases no option to make any backups.

Thats a real hard decision and my own suggestion is go with your heart. You will find the right one that fits your needs. No one service is exactly the same even if they are based off of the same codesets. They each have figured out how to make it their own in a sense.