For single seasons, From 1901 to 2011, For players in the saved report : (Batted .260 or lower, 1980-2010, 27 or younger, 2000 PA), From Age 28 to 99, (requiring Qualified for league batting title), sorted by greatest Batting Average: Results - Baseball-Reference.com.
The actual report above isn't that interesting, but the new feature I used to create it is. When you save a report using the "link url" option under the SHARE link (and you can use this anywhere on the site). This saved report will now appear as an option on the very bottom of the season finders.
So for the report linked above. I first found all of the batters from 1980-2011, ages 0-27, with 2000 PA's and sub .260 career batting averages. I then saved that report, reloaded, used that report, changed the ages to 28+, used single season and then found the best single-season batting averages among this group.
This feature will give you a lot of flexibility. You could save reports like 2000 first round draft picks, or 1999 Chicago Cubs, or anything else on the site. I think this will have a lot of power, but I expect you'll have some ideas I haven't thought of. You will also be limited to 200 players total, so very broad searches may not work.
This is limited also to your last 20 saved reports. Also note that if you use the season finder to save a report and then want to use that report, that will require a page reload to get that widget populated with the new report.
This is live only on the season finders at the moment and you can only filter on players. It would be nice to allow searches that look for year n+1 or allow it for particular games, but at the moment, we are stuck with this method.
Have fun and let us know if there are any interesting reports you create.