1. Reddit:
Reddit is an ocean, The king of all forums! It's basically a forum for pretty much EVERYTHING! Way better than Quora. In Quora; you feel like you're talking to yourself, there's virtually ZERO human interaction (Apart from thumb-ups). But in Reddit, you can have a good chat with people who like the same things you do.
2. Yahoo Answers (Y!A):
It's not a forum but it's a great place to goof around! No one is serious on Y!A, NO ONE! Wonder why tigers don't have 5 legs? Ask on Y!A!
Although it's no longer the place it used to be. Now, very few people actually use it and I think Verizon Wireless (Which bought Yahoo! some time ago) is going to kill it soon.
Here's an example:
3. Twitter:
Twitter isn't a forum, I know. You can't write a tweet larger than 280 characters, I know. But... It's a great place to be once you get some active followers! I use Twitter as a news feed, a replacement for old RSS, and often post about trends.
4. Damadam:
It's a desi website and isn't exactly a forum; more like a chat room full of broken heart romeos and fake Juliettes! Good for passing time but don't expect anything else. Only 14-16 year olds hang around there so conversations can get real boring real fast.
The problem is; most users don't speak and/or understand English there and reading Urdu in English Alphabets is a tiresome experience but worth a shot!