Org-mode is a very useful list outlining application for Emacs, which gives you complete control over your hierarchical data. This major Emacs mode allows you to collapse and show information quickly by pressing TAB and easily and move hierarchies around by pressing Alt-Cursor. Org-mode can quickly export your hierarchical data into other formats, so you need never type HTML again!
Another useful feature is that org-mode also has a mode for easily editing tabular data in text files. The table editor allows you to quickly define a series of columns of data, by delimiting the data with the vertical bar symbol (|). The editor then ensures that all the column data in each row lines up as you tab between fields.
The main web site for org-mode is here. There is a Google talk by Carsten Dominik (the creator of org-mode) on youtube
