Minecraft wiki entry for Drops, associated text: Blocks marked with "T" need to be broken with a specific tool to drop anything (including experience). The Silk Touch enchantment doesn't remove this requirement.
Where noted, Fortune can increase the number of dropped items or multiply it. Increase simply gives 0-lvl extra items. Multiplication happen with the following chances:
Fortune I: 33% * 2 (33% more on average)
Fortune II: 25% * 2, 25% * 3 (75% more on average)
Fortune III: 20% * 2, 20% * 3, 20% * 4 (120% more on average)
Container blocks (brewing stands, chests, dispensers, droppers, flower pots, furnaces, hoppers, jukeboxes, trapped chests and beacons) drop themselves when broken along with their content.
All blocks not listed in the table above drop themselves when broken. Fortune doesn't affect their drop.