Bukkit

v0.9
+ Fixed the conflict caused when both blacklist and whitelist where enabled, only one or the other can now be enabled.
+ Removed some validation that denied none-solid blocks, things like ladders and torches can now have gravity.
+ Reduced the fall delay from 10 ticks to 5 when only on place is enabled.

v0.8
+ updated default blacklist to include NETHER_BRICK, LEAVES_2, ENDER_PORTAL and ENDER_PORTAL_FRAME. Please update your blacklist or delete the list and restart the server to generate the default.

v0.7
+ Config option "enabled-worlds" to enable gravity in only worlds listed. By default world, world_nether and world_the_end will be added. (Suggestion from http://dev.bukkit.org/profiles/warezme/)

v0.6
+- Config options "whitelist-block-ids" and "blacklist-block-ids" are now replaced with "whitelist-blocks" and "whitelist-blocks". The lists no longer supports ID numbers and instead uses Material names to support new versions of Minecraft.
+ New config option "only-on-place" default false, if true the gravity will only apply when a player places a block and if false gravity will apply on each block update. A example of a block update could be a Leaf decaying, an explosion or when you place or break an adjacent block.
+ New config option "clearance" enables control over how many air blocks are required below a block before gravity is applied.

v0.5
+ New config options, whitelist and whitelist-block-ids.
+ If you wish to apply gravity to only a selected block type or list of blocks set whitelist to true and list the whitelist-block-ids.

v0.4
+ New config options, blacklist and blacklist-block-ids.
+ If you wish to prevent gravity being applied to a block type or list of blocks set blacklist to true and list the blacklist-block-ids.

v0.3
+ Added config.
+ Config option to allow items to drop if a block falls to an invalid location. For example onto a touch.
+ Added a scheduleSyncDelayedTask for performance and timing increase. This means you have more time to place a block beneath a block just placed before gravity is applied.

v0.2
+ Added permission node "gravity.apply"

v0.1
+ initial release.

+ Config changes, See change log above.

WARNING - Using a blacklist with the config option "only-on-place" set to false can cause world corruption. To use a blacklist safely please ensure you list common block types like stone and leaves and you could set the "clearance" higher than 3.