I think there should be a potion for almost every item and a good or bad cause and effect, sugar: sugar rush, speed and nausea for a short period of time. dirt, sand or gravel: temporarily mine them faster. glass: you see glass instead of dirt or cobble temporarily. diamond you mine at 4x the normal rate for a short amount of time.
Gold: get fortune 8 for 12 blocks. cake: sugar rush for a longer time than sugar with less nausea.
Snowball: everything you walk on is covered with snow. splash snowball: immediately spawns a snow golem.
wool: you take no fall damage when falling for 30 seconds. string: temporarily have a huge jump boost.
diamond block: be invincible for half a minute.

this is all I can think of at the moment. :)