  We analyse public domain time-series photometric observations of 30 known and
candidate binary post-AGB stars for measuring pulsation and orbital periods. We
derive periodicities for 17 stars for the first time in the literature. Besides
identifying five new RV Tauri type pulsating variables (three with the RVb
phenomenon, i.e. long-term changes of the mean brightness), we find multiply
periodic (or possibly irregular) post-AGB stars on the two edges of the
instability strip. The temperature dependence of the peak-to-peak light curve
amplitudes clearly indicates the changes in excitation as post-AGB stars evolve
through the strip. One object, the peculiar Type II Cepheid ST Pup, showed a
period increase from 18.5 to 19.2 d, which is consistent with the known period
fluctuations in the past. In HD 44179, the central star of the Red Rectangle
nebula, we see very similar asymmetric light curve than was measured 10-15
years ago, suggesting a very stable circumstellar environment. In contrast to
this, HD 213985 shows coherent but highly non-repetitive brightness modulation,
indicating changes in the circumstellar cloud on a similar time-scale to the
orbital period.
