As time goes on, more and more of the old Sun websites and domains are being shutdown and moved across to Oracle systems and domains.
One of the things that has recently moved is the Sun Downloads (the A-Z list). The page exists and all the links are valid, however some of them don't take you to the actual product download. Instead they take you to a generic page documenting the migration.
On this page is a link to an FAQ and the general answers is: if you can't get to a download from the A-Z page, you need to use the "Advanced Search" feature under "Patches & Updates" on My Oracle Support.
For example, this is how you'd find the latest Ultra 20 M2 Tools ISO image:
You should be able to find things like Sun Grid Engine, LDoms, Java Web Console, SunMC, graphics drivers, etc within My Oracle Support.