Title: Things You Should Never Do, Part I (aka Old Code != Bad Code)
Author: Joel Spolsky
Comments: This is an oldie, but a goodie. It is a reminder, to me, why rewriting an existing application can be both a financial and strategic mistake. Sometimes you cannot get around it, but the reasons I can think of have to do with building the applications on top of inadequate frameworks (read: Rewriting Reddit and MySpace moves to ASP.NET 2.0).
Favorite Quote:
There's a subtle reason that programmers always want to throw away the code and start over. The reason is that they think the old code is a mess. And here is the interesting observation: they are probably wrong. The reason that they think the old code is a mess is because of a cardinal, fundamental law of programming: It's harder to read code than to write it.