What are the major changes in the APA Publication Manual from 5th to 6th editions? A lot of journals use APA style for journal article submissions. In 2009 APA released the 6th edition with several changes to the 5th edition. 


What's a good summary of the important changes in the 6th edition?
Or, alternatively, what is a good online resource listing these changes?
If you're going to be submitting articles to APA journals you should have access to the APA Publication Manual 6th edition. And it is useful to use a template (see here for discussion of 6th edition LaTeX packages) and a citation system that supports the rules.

There are changes that permit new things (e.g., longer abstracts, bullet lists, and keywords are permitted, single-spaced tables) and there are new suggestions (e.g., stronger encouragement to report confidence intervals; you can say "subjects" if you want; "I" and "we" are recommended over "the researchers").
However, if you already know the 5th edition, then  changes of particular interest are those  where compliance with the 5th edition would actually lead to violation of 6th edition rules.

Changes that stood out to me:


Provide two spaces at the end of sentences (but this doesn't make much sense if you use LaTeX)
Formatting of headings have changed and are simplified so that five-heading papers have the same first four headings as four-heading papers
Figure captions are now placed on the same page as the figure below the figure.
Tables and figures now appear before appendices
Footnotes are now placed on the same page that they are referenced.
Report p-values to two or three decimal places exactly and those less than .001 as p&lt;.001.


References changes that stood out to me:


Include city and state for book publishers even if city is well known
Provide DOI with any references that have a DOI


General summaries of changes from 5th to 6th edition

Of course there are lots of little changes, check out some of these references for some other reviews of changes and resources:


John Dugan has a good summary of the changes in the 6th edition: mentions changes to end of sentence spacing, running head, headings, bias, repeated citation of same source in same paragraph, recording publisher location, references with 6+ authors, and DOIs.
Ace-editor provides an overview of changes 
The APA has a tutorial on the 6th edition. My preference was to mute the voice over and just read the text.
Sample papers in 6th edition: one experiment paper from APA and a two experiment paper from APA, another example with commentary
The official APA style blog has a few posts on 6th edition changes.
Fairly extensive set of notes listing changes
Jody Davis lists changes
Hughes (2010) et al provide an academic review of the changes.
General set of guidelines on APA 6th edition from Indiana Wesleyan University


References


Hughes, G., Onwuegbuzie, A., Daniel, L., and Slate, J. (2010).
Editorial: Apa publication manual changes: Impacts on research reporting
in the social sciences. Research in the Schools, 17(1). PDF