I've been interning at a TV station and they use Final Cut Pro exclusively (made my Apple, only for Macs). Really amazing program. It's expensive, but there's a cheaper version called Final Cut Express that goes for about $100. If you're using a PC (obviously not since you've been using iMovie, but anyway...) you can check out Avid. They have a whole bunch of different products, but one that springs to mind is XPress DV. Also you can try out their interface with a free version called Avid Free DV. It's about a step up from iMovie.
If you want to use what the Pros use I'd go with Final Cut.
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See my website, Common Sense:
www.ThoseDamnLiberals.org
I'm an atheist/moralist.
My parents were hippies. Both my grandfathers were Mennonite conscientious objectors in WWII. It's complicated.