Created a search plugin to my favourite Mind-mapping tool, FreeMind which itself is open-source Java based.
The existing program had limited search facilities, only the current open map, so wrote plugin to allow search from multiple Freemind maps. It uses Apache Lucene to create an in-memory index then orders the results by a score. You can then click on a result to open that map. Can choose to search the maps you already have open, or to recursively search a directory of your choice.