For editing po-files, the following tools have proven to be helpful
- po-edit (www.poedit.net)
- Virtaal (http://translate.sourceforge.net/wiki/virtaal/index)
In a consolidation effort, the translate tools are useful as well (http://translate.sourceforge.net/wiki/toolkit/index).
I have however not yet found a handy tool to break down a big po-file into files by module.
I've been using the Content Translation module to export po files module by module, which I then put into the source.
Also as you know there is the l10n module that now allows translation of strings right in the web interface!
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