Resizable WinForms controls

So I downloaded RSSBandit, the news aggregator written by Dare and posted on MSDN awhile back One thing that really, really bugged me was that the various panes were fixed size. In other words, I couldn't resize how wide the stuff was on the left, or the percentage of the size in the right panel. I figured I might as well go fix it, since the source code was available anyways.

I thought this should be easy, but apparently it's not. Bear in mind that I haven't really worked with WinForms at all, but I couldn't figure out a way to do this.

Is there perhaps a good library / layout manager that allows this kind of stuff easily?  Or can someone point me to a good resource that talks about this kind of thing?

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