The process you follow would be pretty much dependent on the business logic.
For example, if you have all the data in a database, most likely a SQL Server and currently all the aspx pages are retreiving data from the database and displaying it then you can try the following steps.
You can write scripts in C# or other language,
- Connect to the database and retrieve the necessary data and stored them in variables.
- Create a file using the script and start writing to it.
- Start writing html code to the file (for example, response.write(@"<html><head>");).
- Write the value of the variables to the file.
- Then save the file to a location in the web server.
- You can run the scripts using schedules task or by writing listeners.
This way you can create html files and save them to the server.
You will need to make decision as to how often you run the scripts to generate the html files. You will also need to understand that the data in the pages will be as current as you run the scripts.
How to implement an ajax incremental page loading pattern. http://www.asp.net/learn/ajax-videos/video-118.aspx
There is a very useful utility at http://www.codeplex.com/HtmlTextWriterUtil for converting html to C# code to generate it.