In lucene's contrib we have spellchecking support (index-based spellchecker, directspellchecker, etc).
we also have some things like pluggable comparators.
In solr we have auto-suggest support (with two implementations it looks like), some good utilities like HighFrequencyDictionary, etc.
I think spellchecking is really important... google has upped the ante to what users expect.
So I propose we combine all this stuff into a shared modules/spellchecker, which will make it easier
to refactor and improve the quality.