Im trying to create forum..

[eluser]kurucu[/eluser]
I'm doing something similar, and this is the functionality I'm (wrongly) leaving until last, as it looks like it will be inelegant and difficult no matter what happens.

My thoughts were along the lines of:
- Use a table to track which users have visited which threads, and when they last did that
- Show new posts as those posted within the last X days, and otherwise are newer than the last visit, or in a thread not included in the last visit table
- Hot threads would be those with more than Y posts in the last Z amount of time.
- For some reason I always lay my threads of thought out in bullet points.