This plugin provides a single command, `seznamslov', scraping the online
dictionary at <http://slovnik.seznam.cz>, translating from Czech to
English|German|French|Spanish|Italian|Russian and the other way round.

Seems to work; any bug reports, feature requests etc. welcome (you can contact
the author at <stepnem AT gmail DOT com>).

You'll need BeautifulSoup to use the plugin.

[... and precisely because you need BeautifulSoup to use it, you might also get
into some problems described here (I did, anyway, even though I wasn't aware of
any changes, it just stopped working one day; installing version 3.0.8 fixed
it): <http://www.crummy.com/software/BeautifulSoup/3.1-problems.html>]