MySQL supports natively full text search; many database engines do. However, few databases can match a dedicated search engine library like Lucene. Moreover, even if you do not need the power of Lucene, sometimes you are forced to use a database engine that does not support full text search (like raw CSV files).
It would be nice to be able to combine a true search engine with any database engine.
If you are willing to use Java, then Glen Newton from NRC has the solution: LuSql. It allows you to index with Lucene any database accessible by Java (through JDBC). He says it has been extensively tested. It is open source and free.