I have seen Ryan Bates talk about exception_logger and exception notification. Are there any other good ones to consider? What do you like and dislike about these?
Also
I would highly recommend using Hoptoad. We use the free account for our production system which is plenty fine, and is just a life saver. I find it highly superior to the ExceptionNotifier and ExceptionLogger plugins. It's dead simple to install, and then you get automatic email notification, as well as really nice presentation of the exceptions in their web UI.
But, also, one nice thing is that it doesn't email you every time you get the exception, just the first time, but then it queues up the others, so when you go look at it on the web, you'll see that say it happened 7 times or whatever. This alone is really great in that if for some reason you introduce something that is all of a sudden firing off lots of exceptions, and you have a high traffic site, you won't have now completely inundated your email inbox with the notices.
Another other cool thing is that it integrates with Capistrano deployments, and records when your deployments were done, so this gives you a bit more info, and may be the key to tracking down what is wrong (e.g. you deploy, and then shortly thereafter you start getting notices, you know that the problem is in whatever you just introduced).
Finally, there's even an API to interact with it. Lots of goodness, and it's the only thing I use now - even with a New Relic RPM account, I still use Hoptoad for all my exception notification.