I’ve been using a homebrew web-based (php) calendar system based on GTD for over a year now, and it’s been just the thing for me.

Under the hood is a database of one table: “items”. An item has a text field, a date, a status (done/open) and a type: appointment, to-do, tickler, waiting-for, project, maybe, weekly-recurring, monthly-recurring, yearly-recurring, diary-entry.

New items can be easily created on the web page, and existing open itmes are displayed sorted into lists by type; in addition, each item displayed is a hot link that will pop up a text editor for a text file that can be attached to the item.

The display of each list appropriate for the type: for example, the list of open appointments only shows appointments in the future; the list of open ticklers shows all ticklers until they’re marked as done. Essentially undated types — projects, maybes — are all shown until done, regardless of their posting date. Each item has a checkbox next to it to ‘close’ it.

That’s it, it works and it’s simplified my life immensely. The greatest insight for me of GTD is the idea that if you write everything down, you don’t have to worry about it.