1. Export your bookmarks from Chimera. It outputs an HTML file, which is fine. For OmniWeb, no export is necessery since the bookmarks are already stored as an HTML file.
2. Launch Explorer, select "Organise Favorites" in the Favorites menu, then select "Import Favorites..." in the File menu.
3. Select your HTML bookmark file (OmniWeb bookmarks are stored in Library -> Application Support -> OmniWeb -> Bookmarks.html).
4. All bookmarks have been added to Explorer's favorites in a new folder.
If Safari has already been launched on your machine, it won't import your favorites again. If so, then:
1. Quit Safari.
2. Open the Preferences file for Safari in a text editor (it is located at Library -> Preferences -> com.apple.Safari.plist).
3. Find the key labeled "IEFavoritesWereImported" and change the value from TRUE to FALSE.
4. Relaunch Safari.
Your bookmarks have been transfered in the "Imported IE Favorites" collection of Safari's bookmark library!