In addition to this post you should check out Bovard Tiberi's archive of Battlecode history.
General Battlecode posts
I read a lot of these to motivate myself before my first Battlecode in 2014!
- Cory Li's intro to Battlecode
- Spenser Skates on why to compete in Battlecode (if down, see archive version here)
- A post on Battlecode by Greg Little, infamous for some of the hacks he describes there
- Cory Li on bytecode optimization for Battlecode
- My suggestions for how to win Battlecode
- My post on Battlecode coding idioms
Posts from specific years
Here are links to post-mortems and code repositories from Battlecodes past.
- Winning team gtg ice skating lessons' strategy report. (I'm hosting this myself; the original here seems to be down.)
- Winning team My Archon Died BellmanFording the Stream's strategy report. (I'm hosting this myself; the original here seems to be down.)
- Steve Arcangeli's post-mortem as a member of the 2011 winning team gunface
- Steve Arcangeli's code snippets
- A nice post on Battlecode 2014 by David Westreicher of team schnitzel
- My recollections as 2014 winner that one team
- My code repository, which contains links to other 2014 repositories
- Mike Szumielewski's (team MunichSquad) Battlecode 2015 recap
- Posts on Battlecode 2015 by team The Simple Soldier
- Battlecode 2015 postmortem by team Proelium codice Maleficos
- My post-mortem as 2015 winner the other team
- My code repository, which contains links to other 2015 repositories
- A post on Battlecode 2015 by team Smooth Criminals
- Battlecode 2015 postmortem by team Elder Wand
- A post on Battlecode 2015 by Michael Flynn of team Darkpurple
- My post-mortem as a member of the winning team future perfect
- Strategy report from 2nd place team F=<-sin(theta)/r , cos(theta)/r> aka Polar Vortex
- Battlecode 2016 postmortem by KC Power Team
- Battlecode 2016 recap by Merlin's Pants?
- zden, Bovard Tiberi's random map generator for Battlecode 2016
- archon, Bovard Tiberi's bot testing tool
- Code with linked strategy report from winning team smite
- Code and post-mortem from 3rd place team CitricSky
- Postmortem from 8th place team Big Red Battlecode
- Postmortem by finalist NP-cgw
- Postmortem by strong non-finalist and long-time Battlecode competitor Oak's Last Disciple
Battlecode software from previous years
You can still download the last few years' versions of Battlecode and try them out. There are even recorded lectures and example code to help you out. If you are planning on doing Battlecode for the first time, a little practice on a previous year's competition can help you get a running start when the new game is released. While the game changes from year to year, the API is fairly stable and many of the problems you need to solve are the same each year.
The OpenCourseWare site for Battlecode 2013 has everything you need to try your hand at the 2013 competition, including the game software and specs, an example player, and recordings of the course lectures.
In Battlecode 2014 the goal was to herd cows into pastures and get 10 million giga-gallons of milk before the other team, while sending soldiers to shoot the other team's cows and blow up their pastures.
The 2015 competition was a pretty standard RTS game: you had to go out on the map and mine ore to make units to attack and destroy the enemy HQ.
Even older Battlecode gameplay specs
Here are the gameplay specs for the Battlecode competitions all the way back to 2001, the first year of Battlecode. Before 2007 Battlecode was called Robocraft. Thanks to Alex Chen for these links.
Here are some articles about Battlecode in The Tech, MIT's student newspaper. Thanks to Dan Gulotta for these links.