I have been playing with both the iHttpHandler and iHttpAsyncHandler lately, and I came across some interesting information.  There are a couple of blog posts out there explaining when to use one over the other (see Mads Kristensen’s post here, or Vlad Hrybok’s post here)
So when does it make sense to use Async?
Consensus seems to [...]

In the post below I am going to run down a short-list of some of the less-popular performance tips and the reasoning behind them.  There are loads of blog postings and articles on asp.net performance enhancements, and I urge you to check those out as well.  Onto the good stuff…
Session.ReadWrite versus Session.ReadOnly
It goes without saying [...]