WebmasterWorld.com is the industry forum I use anymore. I like it because it is easy to navigate and pretty clear and concise. There are, of course, a couple of areas where I think readers (lurkers) could be brought into a more engaging means.
1. Ability to assign a star to a topic you like. This way you don't have to flag it but you can still show your appreciation. Posts with a lot of stars would obviously show readers that it's a good post and worth the read. This comes in handy especially if the posts are long.
2. Avatars & expanded Bio's that show in posts would be nice. Since the web is lurching toward Social Media, it makes sense to add that sort of profile sense to forums which are one of the original methods of social media.
3. Embed images & video. There are a lot of really great resources out there by way of image and video that would allow authors to more easily express a point of view through that means of example. I'd love to see it.