In a recent post to the NETTUTS.com site Juan Mellado looks at creating caching that will fit in with your a data access layer in your application.

Dynamic web pages are great; you can adapt the resulting page to your user, show other user's activity, offer different products to your customers based on their navigation history, and so on. [...] In this tutorial, I will demonstrate a way to improve performance, without running extra unnecessary queries. We'll develop a query caching system for our data layer with small programming and deployment cost.

He breaks it up into a few different sections:

• The Data Access Layer
• Planning our Caching Scheme
• Static Caching
• Caching Expiration
• Different Expiration
• Some Caveats
• A Benchmark

That benchmark section there at the end mentions that, while caching can help increase page load times, it's not a silver bullet to solve the problem of bad code. Their solution, however, increased the average request time from about four pages per second up to around twenty-five pages per second.