Photos in Photoshop are too dark on Mac, can't see details?

I'm just starting in digital imagery and I've been playing with Photoshop for a while on my iMac (previous model) and found that all the photos are quite dark and have good contrast on my screen but when viewed on another machine or iPhone 4 become rather flat. I can understand Mac and Windows have different default gamma values but my main problem is that I can't even adjust contrast with Curves or Levels, cause the pictures are already so dark on my screen! So when I start to play with the curves photos turn into a complete dark mess. I think I could solve that problem somehow by viewing my photos at 100% but that's not quite practical for me. I tried to calibrate the monitor with an in-built plug-in to make the things a bit lighter, but still have problems and the native calibration preset on my machine gives me even darker results. Does anyone know how to tackle that annoying thing?

Regarding the display, check the brightness level and see if you can increase it. In Photoshop use the Shadows/Highlights adjustment (Image > Adjustments), so that the details of the images become more visible.

Http://www.photoshopessentials.com/photo-editing/histogram/
http://www.dummies.com/how-to/content/how-to-use-the-histogram-panel-in-photoshop-cs6.html
You're probably better off learning how to read a histogram. No matter how accurately calibrated or out-of-whack your monitor may be, the histogram has an objective view.

Color profiling issues (Cmd+Option+K) may still have an effect on how the image looks, although you have the option of turning off color management. At the moment, Photoshop is one of the few programs that use color profiles. Web browsers currently ignore these, though some may be planning on better support. Other image-using programs might never rely on profiling. For casual purposes, turning off color management can ironically help keep a consistent look across systems.