I was just researching Median on SQL Server last week. Here is a good series of articles from some very qualified folks where a back-and-forth discussion broke out on the topic about which method was fastest:

1. December 15, 2006 - Aaron Bertrand blog showing Itzik Ben-Gan method for finding median: http://sqlblog.com/blogs/aaron_bertrand/archive/2006/12/15/428.aspx

2. December 18, 2006 - Adam Machanic blog showing a Joe Celko method faster than Itzik Ben-Gan's method: http://sqlblog.com/blogs/adam_machanic/archive/2006/12/18/437.aspx

3. December 20, 2006 - Peter DeBetta blog entry showing a revised Itzik Ben-Gan method is faster than the Joe Celko method: http://sqlblog.com/blogs/peter_debetta/archive/2006/12/20/Medians_Actual_Query_Cost_and_Statistics.aspx

And here is a buffet of methods from Celko for cross-reference:

- April 05, 2009 - T-SQL median adventure with Celko: http://www.simple-talk.com/sql/t-sql-programming/median-workbench/