Seetxt is a lightweight, configurable text file viewer for linux with some unique features. It maintains "document meta-data" for each user, allowing them to keep bookmarks and highlights for read-only system files, such as unix manual pages (which are presented as they would be via the man command). It also has a "server mode" so that command line requests can be sent to a single running instance, similar to most web browsers and many editors; this makes seetxt handy for use as a default action for text files with your file browser. There's also multi-layer regular expression searching, hyperlinked apropos searches, content processing via shell commands, and a history list.
The latest version of seetxt is 0.72, released December 2010. Binary versions for many platforms are packaged by Debian.