GNUstep is a cross-platform, object oriented environment composed of frameworks, tools, and servers (daemons). It is very similar to the Cocoa frameworks from Apple, and tries to maintain compatibility with Cocoa wherever it is desired and possible. The frameworks provide classes for containers, distributed objects, object archiving, file management, text system, font management, image composition, WYSIWYG PostScript graphics, and more.
Haystack is a powerful tool designed to enable each and every individual manage all of her information in the way that makes the most sense. By removing the arbitrary barriers created by applications that only handle certain information "types", and recording only a fixed set of relationships defined by the developer, users can define whichever arrangements of, connections between, and views of information they find most effective. Such personalization of information management will dramatically improve your ability to find what you need when you need it.
muCommander is a cross-platform file manager with a dual-pane interface that features support for FTP, SFTP, SMB, NFS, HTTP, Amazon S3, Hadoop HDFS, Bonjour/Zeroconf, email attachments, archives in many formats (including Zip, RAR, 7z, GZip, Tar, Bzip2, ISO, NRG, AR, Deb, and LST), bookmarks, credential management, themes, multiple windows, full keyboard control, and many configuration options. It is available in 23 languages.
Doodle is a desktop search engine for Linux. It searches your hard drive for files using pattern matching on meta-data. It extracts file-format specific meta-data using libextractor and builds a suffix tree to index the files. The index can then be searched rapidly. It is similar to locate, but can take advantage of information such as ID3 tags. It is possible to do full-text indexing using the appropriate libextractor plugins. It also supports using FAM to keep the database up-to-date.