For the full list of changes, please take a look at GitHub:
https://github.com/TShock/TShock/commits/master
From now on, all release notes aren't put here. It's too much to track, but new features will be tossed here.

Changes in API release 3:
 - Added support for SQLite
 - Added support for MySQL
 - Added /user command, supports adding users via in game command
 - Added database editor for editing the MySQL + SQLite DB systems
 - Fixed /region list and /warp list
 - Fixed Jexius's font exploit
 - Added /annoy
 - Added canbuild permission
 - Fixed mysterious chair rotation system
 - Added /ip <player> to retrieve a player's IPv4 address
 - Removed /buff
 - Added command line paramater -worldpath, which changes the location where Terraria checks for worlds
 - Fixed save world race conditions
 - Added /login <username> <password>
 - Fixed an instance where NPC.maxSpawns was incorrectly referenced in favor of NPC.defaultMaxSpawns
 - Chests are ignored from kill tile abuse
 - Added /reply (/r) to reply to a /whisper
 - Fixed /broadcast spacing
 - User names and passwords are now accepted. Passwords are hashed with SHA512
 - Added MaximumLoginAttempts to configuration
 - Added /tphere * and /tphere all
 - Added /auth-verify to verify and turn off the auth code system
 - Added the ability to Log/notify admins when commands are executed. 
 - Added a new Configuration Flag called "DisableBuild".
 - Added command to toggle anti-build.
 - Added -ip commandline 
 - Fixed hair exploit 
 - Added /rules, reads from ./tshock/rules.txt
 - Added AdminChatPrefix configuration option.
 - Added ForceKillAll to kick all players.
 - Added support to spawn all types of slimes (have to use the full exact name)
 - Added /king to spawn king slime. 
 - Adds protected regions. Use /region help ingame for extra help
 - Added warps to tshock, edited some region commands 
 - Added the ability to ban specific items for being in inventory when joining server
 - Added /setspawn command,Sets the spawn point of the server
 - Added HardcoreOnly 
 - Sandgun and Dirt Rod no longer triggers a Impossible to place block. 
 - Added /displaylogs. Toggles log output to player who executed the command.
 - Added -configpath command line parameter to set config path. 
 - Added broadcasting on map saves
 - Added /tphere * and /tphere all 

Still Lots More To Add! :)

Changes in API release 2.0.0.0:
 - Added update checker.

Changes in API release 1.8.0.0:
 - Added permissions system for managing different levels of admins
 -- Added one time auth system for new permissions. When you start the server and load the map, you get a one time auth code. Use /auth <code> to become superadmin.
 - Check the wiki on Github for more information on Permissions.
 - Fixed BanExplosives not doing anything.
 - All ban lists have been consolidated into one file, where reasons, IPs, and player names are stored together.
 - Fixed spawnrate and max spawns

Changes in API release 1.6.0.0:
 - Added spawn protection
 - Fixed numerous bugs
 - Added a few commands

Changes in API release 1.5.0.1:
 - Fixed cheat detection

Changes in API release 1.5.0.0:
 - Added /time
 - Added /kill <player>
 - Fixed /item
 - Added /slap <player> [dmg]
 - Added broadcast event for kill tile abuse
 - Fixed teleport somewhat
 - More cheat detection
 - Extended new cheat protection to mana
 - Update player exploit patched
 - Fixed /spawn
 - Made /invasion a toggle

Changes in API release 1.4.0.0:
 - The configuration file is now located at config.json
 - Something else.

Changes in API release 1.3.0.1:
 - Re-coded the entire command system
 - Re-coded the help command
 - Implemented what seems to be the most recurring blacklist ever

Changes in API release 1.3.0.0:
 - Added /maxspawns
 - Added /spawnrate
 - Resetup the configuration file to read spawn rate information.
 - Patched the ability for clients to spawn NPCs
 - Patched the ability for clients to rewrite the server through SendSection
 - Make sure to use this Terraria.exe for the server: (http://dl.dropbox.com/u/29760911/Terraria.exe)
 -- Allows spawn rates to be changed

Changes in API release 1.2.0.1:
 - New update system

Changes in API release 1.2:
 - Added /butcher
 - Added /heal
 - /spawnmob now takes another argument for the amount
 - /item now adds items to the inventory directly
 - This update credit to Deathmax

Changes in API release 1.1:
 - Added /tp
 - Added /tphere
 - Added /spawnmob
 - Added /item
 - Fixed /spawn
 - Updated /help
 - Everything in this update credit to Deathmax, High, and Shank

Changes in API release 0.1:
 - Added /save to save the world
 - Added /spawn to teleport to spawn
 - Added broken teleport stuff
 - Major re-write of the anti-tnt code (now uses a blacklist instead of a whitelist)
 - Fixed server crashing bug of the anti-tnt code
 - Made the anti-tnt code decrease the threshold instantaniously
 
 Re added the update checker.