-ness:
* happy (adj.) -> happiness (noun)
* sad (adj.) -> sadness (noun)
* good (adj.) -> goodness (noun)
-ity:
* cruel (adj.) -> cruelty (noun)
* real (adj.) -> reality (noun)
* pure (adj.) -> purity (noun)
-ty:
* pretty (adj.) -> prettiness (noun)
* empty (adj.) -> emptiness (noun)
-ship:
* friend (adj.) -> friendship (noun)
* partner (adj.) -> partnership (noun)
* leader (adj.) -> leadership (noun)
-dom:
* free (adj.) -> freedom (noun)
* king (adj.) -> kingdom (noun)
* wise (adj.) -> wisdom (noun)
-hood:
* child (adj.) -> childhood (noun)
* man (adj.) -> manhood (noun)
* knight (adj.) -> knighthood (noun)
-er/-or: (This one is trickier, as it sometimes forms a noun from a verb, but it can also be used for adjectives):
* fast (adj.) -> faster (noun) (refers to someone who is fast)
* young (adj.) -> younger (noun) (refers to someone who is young)
-ance/-ence:
* important (adj.) -> importance (noun)
* silent (adj.) -> silence (noun)
* confident (adj.) -> confidence (noun)
Important Note: Not every adjective can be turned into a noun using these suffixes. Some words just don't work that way.