http://en.wikipedia.org/wiki/Upsert
Insert Update stored proc on SQL Server
Is there some clever way to do this in SQLite that I have not thought of?
Expanding on Aristotle’s answer you can SELECT from a dummy 'singleton' table (a table of your own creation with a single row). This avoids some duplication.
I've also kept the example portable across MySQL and SQLite and used a 'date_added' column as an example of how you could set a column only the first time.
REPLACE INTO page (
id,
name,
title,
content,
author,
date_added)
SELECT
old.id,
"about",
"About this site",
old.content,
42,
IFNULL(old.date_added,"21/05/2013")
FROM singleton
LEFT JOIN page AS old ON old.name = "about";