What is the best day and time of day to publish app (or its updates) to the Market? What have you found to work best and generate maximum number of downloads/sales?
The best time to submit/update an app is when most potential users are active but the fewest number of apps get deployed by other developers. To determine the amount of games that get published (and thus appear in the "Just in" list) I monitored the Android Market with a script for two months. I also looked at the time one of my games get started for the first time over several weeks to approximate the time games get installed.
Combining both aspects I assume that you should submit your app in the evening (GMT). In addition, publishing at the weekend is better than publishing on weekdays. However, publishing today is obviously better than publishing weeks later because users can only install published apps ;)