Convert rich text to plain

I have a rich text field which can be quite long. I'd like to display truncated versions of it in some report views. I'm not aware of a function for converting rich text to plain (that is, stripping out HTML characters). When I use a simple formula like Left, the problem is that this will frequently break the long field, because closing tags won't be part of the truncated value. So the truncated version becomes something like 

<span>The lazy brown fox jum

Any ideas how to strip out HTML (rich text tags)?

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Jonathan Heuer
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