Version 2 of Searcharoo is now online (although still in final draft form) and I'm starting to think about the version 3.
The first priority is building a database and/or file-based persistance layer, but other more advanced search-type technology is also on my mind, including STEMMING :
What is Stemming?
Paice/Husk stemmer modifications by Antonio Zamora
Limitations of Stemming
and for Japanese text (which I'm also interested in)...
A WWW JAPANESE DICTIONARY and article 2
The Challenges of Intelligent Japanese Searching