Rob Bradshaw, of the ever-helpful BiblicalStudies.org.uk, has recently posted the following article:
With the necessity to consider the view that the Pastoral Epistles are pseudepigraphal (or perhaps “allonymical”?), the article — which I have not read — sounds like one to read.
Note that Guthrie is the author of the Tyndale New Testament Commentary on the Pastoral Epistles.
Update (2006-12-12): I’ve read the article now and can recommend it. Guthrie unsurprisingly concludes that those who support a theory of canonical pseudepigrapha have built upon a shoddy foundation. Well worth the reading.