Recently, I posted a roster review of the 1967 Cardinals on my 1967 baseball cards blog. After examining each player and each game they played, with the help of Baseball-Reference.com (for starting lineups) and Retrosheet.org (for every game played by each player - which is easier to verify the non-starters than by pulling up each game's boxscore in Baseball-Reference.com), it seemed like the Cardinals had 26 or 27 players on their squad during April and May.
Reader Patrick Farrell pointed me in the direction of an internet newspaper archive, and specifically, columns in some of the Florida papers on May 11, 1967.
Below is the transactions column from the Sarasota Herald-Tribune on May 11, 1967, which lists the players released or sent down as all teams scrambled to get down to the 25-man limit that late into the season. I wonder why this wasn't required by opening day? Does anyone have insight into this?
In my earlier review of the Phillies, I also noticed that they seem to have had 26 players on their roster in the early months, before Tito Francona was sold.