The site http://www.manageability.org/blog/opensource/ contains a wonderful collection of Collections of interesting Open Source projects written in Java. Yes, collections is duplicated on purpose. The site presents a list of Open Source projects for each of a long list of categories, such as:
- ETL (Extract Transform Load)
- Document Management
- Web Crawler
- XML Diff
- Rule Engine
- Text Search
- HTML Screen Scrapers
The article How to Choose an Open Source Library provides some very useful guidelines for choosing the right Open Source library – not so much on functionality but looking more for stability, maturity en future-proofness.
One Open Source project I was previously unaware of, is named a very likely winner in the open source arena: Daisy
Daisy is a comprehensive content management application framework, consisting of a standalone repository server accessible through HTTP/XML (using the ReST style of WebServices) and/or a high-level (remote) Java API, and an extensive browsing and editing DaisyWiki application running inside Apache Cocoon. Daisy is licensed under the commercially-friendly Apache License 2.0. Outerthought provides commercial services around Daisy. More marketing talk can be obtained from their website. This is the Daisy community website, with access to downloads and the full documentation. Enjoy!