I'm Not Getting My e-mail Notifications!
The first thing you need to do is ensure your e-mail that the notifications are going to is correct and is validated. (I don't know how to check this status...but I know mine *is* validated...can someone add how to check it?)
Then check your desired notification settings at http://www.livejournal.com/editinfo_do.bml If not, select the proper notifications and hit "Save changes".
If you're still encountering the problem, on that same page, uncheck the "Send HTML e-mails" and save changes once again.
If none of the above works, and you're not past (grammar check?) your e-mailbox size allocation, then it is very likely the problem is on your receiving mail server's end. Investigation has shown that a large percentage of the problems relate to the spam filters on a program called "sendmail", although users on AOL and other companies that don't use sendmail are experiencing this problem as well.
Check with your ISP/mail provider and ask if they are filtering out LiveJournal posts. If they are, impress upon them that your notifications are not spam and perhaps they can/will make the changes on their end to enable the messages to go through. (This may need to be reworded...?)
Failing all that, Hotmail users report they are still getting their notifications. (This should probably have some extra information, or different information...or something)