This feature is extremely important - many users have tons of cliparts in this format (and in CMX format).
Valek Filippov created simple C-based parser which extracts preview picture from CDR files.
We started using cdr2svg.py script provided by Richard Hughes. Of course such script name is an overstatement because this code can parse CDR chunks for 12 version only and at least in my testing fails during parsing.
After small refactoring we improve this parser: CorelDRAW files from 5 up to 13 versions can be parsed. More over CMX files of all versions are useful for parsing too :). Output sample here.
Using these results we can figure next summary:
CDR file format can be reverse engineered.
Using this experience we can improve CMX import for latest CorelDRAW versions
Also this info can be useful for CDR/CMX file preview (for example, in Konqueror)