The paper presents combined spectroscopic and photometric orbital solutions for four close binary systems: SW Lyn, QW Gem, AP Leo and V2150 Cyg. The photometric data are new, while the spectroscopy has been recently obtained within the radial velocity programme at the David Dunlap Observatory. This paper is the first in the planned series of investigations. We give an extensive description of the motivation for the series and of the main assumptions made in our solutions. The four targets of this investigation span a range of typical configurations and thus present different levels of difficulty for the combined spectroscopic and photometric orbital solutions.

Recent highlights of our study of positive and negative superhumps in cataclysmic varibles are briefly reviewed. The ``genuine" superhumps have been detected a day after the unexpected superoutburst of WZ Sge, when the orbital variability dominated the light curve. TT Ari has shown an unprecedented switch form the usual negative superhump state to the positive state with an excellent coincidence between the observed and theoretically predicted period values. Both stars show evidence for variability at a time scale of 20 minutes. The superhump period of RZ LMi has been corrected based on the observations of the superoutburst in 2001. ES Dra shows no evidence for prominent superhumps, possibly indicationg its low inclination. However, the superoutburst has shown a splitted maximum with a separation of 20 days. The ``superhump period-luminosity" dependence has been detected for two cataclysmic variables of different types -- the nova-like BZ Cam and the UG SU star V368 Peg.

We report the results of the second large campaign of photometric observations for the small-amplitude delta Scuti star GSC 4778-00324, detected in the course of a multi-site campaign aiming at monitoring V1162 Ori. We confirm the presence of the same two frequencies as found in the first analysis based on the 2000-2001 data.

The first complete I-filter light curve of the eclipsing sdB binary HS 0705+6700 is analyzed using the Wilson-Devinney code and new geometric and photometric elements are derived. Using these elements together with the available spectroscopic data, it was possible to build a detailed model of the system. Our results are in good agreement with those found from photometric studies in other bands.

Optical Interferometry can play an important role in modern astronomy. Extrasolar planet and binary star research, are some of the fields, where we will face important discoveries in the future. For the VLTI this will be a real challenge, since it will be the pioneer in angular resolution. In addition, high flux sensitivity will help detecting not only Jupiter-sized planets, but Earth-sized planets too. The ability of the VLTI in detecting new planets, measuring stellar diameters and stellar proper motions, with the use of such techniques, is presented.