Exporting From OmniOutliner
To export the outline to a different format, choose Export... from the File menu and choose a format and location for the file. Currently all rows are expanded when exported. (We hope to add options to export either all of the rows or just the selected rows, and to either expand all of the rows or leave them as is.)

Here are the formats available for exporting:
Plain Text (with tabs) (.txt) - The first line has the column titles, while the remining lines start with tabs to indicate their level, followed by the bullet strings (as configured in the Text Export preferences), and then the text of each column, separated by tabs. This format ignores the status checkboxes.

Tab seperated text is suitable for exchange with other programs. For example, you can load a single column outline into Word, and have Word autoformat it into an outline. If you only have a table of information then you should be able to export in this format and load the result into spreadsheets.
Plain Text (fixed width) (.txt) - This generates formatted text that is suitable for viewing. You can set the character width used by each column in the Column Export Width panel available from the Show Info (⇧⌘I) menu item under the Format menu. Fixed width export uses the Text Export preferences for the bullet and checkbox strings. This is also the text format used when you copy and paste items.
Plain Text (MORE 3.1) (.txt) - This generates a Plain Text document that MORE 3.1 can load, preserving the outline. Each line has tabs to show the rows level, followed by '-' and two spaces. Status checkboxes are not represented in the generated file.
HTML (HyperText Markup Language) (.html) - This uses unordered lists for single column outlines, and tables with column titles for multiple column outlines. Font and color information is preserved, and the status checkboxes are included if they are visible in the outline.
RTF (Rich Text Format) (.rtf) - For single column outlines it uses rulers to control the left edge of each row, and the placement of the bullets, checkboxes, and start of the text. It tries to preserve the rulers that may have been used in the row of the outline, but can't preserve the first line head indent. You can easily edit the resulting file in TextEdit and have it rewrap the lines.

For multi column outlines, OmniOutliner makes extensive use of rulers to preserve the columns in the resulting file. It tries to preserve the rulers that may have been used in the rows of the outline, including the first line head indent. This looks good in most cases, but when you have text of different sizes you can get cases that look odd. The file that is generated is not really suitable for editing because the text has been split up into separate rows and columns. It's also not good for pasting into Mail.app since it doesn't preserve the rulers — you can attach the RTF file to the message, though.

You can customize the RTF that is generated, including the bullets and checkboxes, in the RTF Export preferences.
Related Topics
Table Of Contents: Advanced Topics
Importing From Other Applications