If you are a CCD observer the Universe is your oyster. Nearly all the AAVSO program stars can and should be observed with CCDs and science filters. The primary advantages of CCD detectors over visual observers are the potential for very high precision photometry, which facilitates detecting very minute light changes, and the ability to record much fainter stars.
Long Period Variables
There are many Long Period Variables (LPVs) whose range exceeds the normal limit of visual observers. Adding CCD observations to fill in the faint part of the cycle is a useful and necessary thing to do. Miras with minima fainter than 14th magnitude are ideal targets for CCD observers.
There are a number of LPVs that have strange humps or bumps in their light curves. These stars' light curves may benefit from additional higher cadence CCD observations to record the changing nature of the bumps each cycle. For more information see the LPV section web page on LPV Humps .
LPVs with close companions that mask the true behavior of the variable star can also be a challenging set of targets for CCD observers. Obtaining acurate data may require special techniques such as psf fitting.
Short Period Pulsators and Eclipsing Stars
All the eclipsing binary and RR Lyrae data collected by the AAVSO now is CCD data. Other pulsating stars, especially those with small amplitudes, such as Cepheids and Delta Scuti stars, are best observed with the precision CCDs and computers provide. To find out what specific projects are currently ongoing or to obtain lists of stars of interest see the pages of the Short Period Pulsator section  and the Eclipsing Binary section  or contact the section leaders.
Superhumps in cataclysmic variables (CVs) and quasi-periodic fluctuations are among these. CVs in quiescence are generally very faint (16th-20th magnitude or fainter) and therefore beyond the reach of most visual observers. The pages of the Cataclysmic Variable section  keep observers informed of recent activity, interesting new stars and lists of campaign stars such as the Z CamPaign , the Long Term Polar Monitoring Programme  and the Hamburg Survey CVs .
Novae and Supernovae
Galactic novae are very interesting to astronomers and they continue to observe them for years after the initial eruption. Recording these outbursts and the subsequent years long fading to faint pre-outburst levels is a very important set of observations that can only be done with CCD detectors and diligent observers. Obtaining light curves for eruptions of extra-galactic novae in the Andromeda Galaxy (M31) and the Large and Small Magellanic Clouds is a challenge many amateurs can meet nowadays also. Any Type IA supernova that erupts to 15th magnitude or brighter should be considered fair game for CCD observers.
With all these stars the object is to obtain enough data to build a long term light curve showing the fading trend from maximum light to pre-outburst levels.
Extrasolar Planet Transits
A new and exciting challenge for CCD observers is in recording the light curves of transiting exoplanets as they cross in front of their parent star from our point of view. This requires a high degree of precision photometry, but is well within reach of many CCD observers.