I've found the package dRedging to be useful for quickly comparing AIC
values between all of the models in your workspace. However, I haven't
looked at it in too much detail, as I have to use an "n-effective" term
instead of the more standard n with my avian nest survival models (a
form of binomial glm). So, I just use dRedging to get a rough idea of
how the model suite is stacking up, before focusing in on the
competitive models.
The package doesn't seem to be on CRAN, it can be found at:
http://www.zbs.bialowieza.pl/users/kamil/r/
If others find problems with it, please share this information.