We present high-speed photometric observations of 20 faint cataclysmic variables (CVs) selected from the Sloan Digital Sky Survey (SDSS) and Catalina catalogues. Measurements are given of 15 new directly measured orbital periods, including four eclipsing dwarf novae (SDSS 0904+03, CSS 0826−00, CSS 1404−10 and CSS 1626−12), two new polars (CSS 0810+00 and CSS 1503−22) and two dwarf novae with superhumps in quiescence (CSS 0322+02 and CSS 0826−00). Whilst most of the dwarf novae presented here have periods below 2 h, SDSS 0805+07 and SSS 0617−36 have relatively long orbital periods of 5.489 and 3.440 h, respectively. The double-humped orbital modulations observed in SSS 0221−26, CSS 0345−01, CSS 1300+11 and CSS 1443−17 are typical of low-mass transfer rate dwarf novae. The white dwarf primary of SDSS 0919+08 is confirmed to have non-radial oscillations, and quasi-periodic oscillations were observed in the short-period dwarf nova CSS 1028−08 during outburst. We further report the detection of a new nova-like variable (SDSS 1519+06). The frequency distribution of orbital periods of CVs in the Catalina Real-time Transient Survey (CRTS) has a high peak near ∼80 min orbital period, independently confirming that found by Gänsicke et al. from SDSS sources. We also observe a marked correlation between the median in the orbital period distribution and the outburst class, in the sense that dwarf novae with a single observed outburst (over the 5-year baseline of the CRTS coverage) occur predominantly at shortest orbital period.