Sharepoint - Add printer-friendly functionality to SharePoint 2010

We usually use print style sheets (<link rel="stylesheet" href="print.css" type="text/css" media="print" />) to do this.

Check this guide:
http://www.webcredible.co.uk/user-friendly-resources/css/print-stylesheet.shtml

I know Muhimbi has a good third party PDF generator, but I havent tried it.

It is not a good option if you require generic print functionality but SQL Reporting Services is great for building custom reports and it comes with different built in export functions.

However it requires some extra work eg. you need to build your reports separately, you need to take care of integration etc. so maybe it is overkill for your requirements.

Some additional info:

Overview of Reporting Services and SharePoint Technology Integration

For printing Lists you can use the http://spprintlistbutton.codeplex.com/.