For years, I have been using SM3CER Contest Service for HF contests.
It is always good to have a backup, so I am looking for more or better.
What do you recommend?
I use the WA7BNM Contest Calendar, usually the 8 Day version is enough for me, I can't plan much farther in advance. This one is nice with links to the rules and such so I check it regularly. There is also the ARRL Contest Calendar, it usually only has the ARRL sponsored contests though. And there is always the handy 3830 Scores site for the post contest chest-beating :). But the quickest way to get a sense of how you did.