First, as a CYA, I don’t endorse any of these products so take my opinion with a grain of salt.
I see this a lot on the MSDN forums as well as pretty much every client wants as well. So the question is always the same, either they don’t like the out of the box SharePoint forums, or the out of the box SharePoint forums don’t meet their specific needs.
First, before I mention ANY 3rd party options, etc. just keep in mind that most likely no one solution will meet your specific needs, most likely it will only meet a most or only a few of them. Therefore my recommendation up front is this: if you have specific needs, or detailed needs, have a look at the 3rd party options, but I think most likely you find that writing your own custom forums for SharePoint will be your best option, although its not exactly an easy process.
To my knowledge, below are your main options that don’t require you to code anything, just buy it or download it install it, and your all set..
SharePoint Forums Project
Cost: Free (as is, no support)
My Thoughts: I’ve personally used this on a project with mixed results. I would say the downfalls of SPForums are more due to the client specific needs than SPForums. The client wanted NTLM, FBA, and anonymous access to the forums, and SPForums just wasn’t built for that. It did work as advertised for NTLM so I give it props for that. Also, all the code is given, so you can modify it to meet your specific needs. I think I modified it to allow attachments and it wasn’t all that difficult to do so. It also had a so so administration interface as well. All data for the forums was stored in backend hidden lists inside of SharePoint which was nice because there was no extra DB dependency.
KwizCom SharePoint Forum WebPart
Cost: Contact KwizCom
My Thoughts: I haven’t personally used this one, but frankly nothing on their website looks-wise makes me want to run out and try this. In addition, they bundle it with this web part “bundles” which makes me really wonder how good the forum is if its offered in their bundles, seems almost like its an after thought to them. Again, I haven’t used it, so don’t take my word for it. As with most vendors though, they have a trial that you can download and try.
Lightning Storm Forums for SharePoint
Cost: Contact Lightning Storm (according to their site, $600.00)
My Thoughts: Based on pure looks/functionality, this looks like probably the one that I would actually pay money for if I were to use it. In addition, they offer a trial download, so if you have questions about it, you can always try before you buy.
DataSprings MOSS Forums Web Part
Cost: ??? couldn’t tell from website
My Thoughts: As with the KwizCom web part, nothing visually attracts me to this forum but their feature set looks promising and seems to touch on most of the hot button forum features. The benefit I see here is that it looks to take on the style of the site your own, so if you use different themes/styles, this web part MAY inherit that. They also offer a trial of the web part.