Robert Murphy, an excellent economist and writer, writes some criticisms of Krugman's recent columns. In the first one, Murphy writes about Krugman's "solutions" to current budget woes. Definitely worth reading.
In the second article, Murphy explains how Krugman mistakes a Keynesian "identity" on trade with real-live economic analysis. Again, another piece worth reading.
On another note, I am traveling these next few days and will post when I can. Of course, Friday is a day of a regular Krugman column, and I am sure he will not disappoint.