I now tried pdfsync and can't get it to work.
I have my preambel and include all my chapters with input. After typesetting, I highlighted a word with an included file and used "Show in PDF-Viewer (pdfsync)", but nothing happens. How ould I get this to work, so that I can jump from the code to the pdf and vice versa?

Thanks in advance
I don't believe that the pdf viewer included inTextMate works with pdfsync.  Try using Skim.   Go to Latex preferences and set "view in" to Skim.  In Skim preferences, set Sync Preset to TextMate.   That should do it!