What are your favorite open source or free library for .NET Charts and Gauges? [closed]

Question

For a in-house hardware monitoring utility, I need to use gauges and charts to help visualize various metrics. Is there any good open source or free charting and gauge library available for .NET? I am not interested in purchasing any components (which excludes components such as Dundas Charts & Graph, which I know would do the job, but would not fit in our budget).

Edit: I also know about Google Charts API. The actual application needs to work without an internet connection, so it is out of the question in this particular case.

Answer 1

I know this isn't open source, but it's worth noting that Microsoft just released a free charting pack for ASP.NET and WinForms. More details here.