I started to use Photoshop Elements which is very good for creating panoramas from multiple images. These days I use Lightroom more since I want to tweak the images I've taken. I also use free apps like Luminance to create HDR images (High Dynamic Range).

If you have a Google account, they have now incorporated many of the features from Nik software in their Android/Online Photo editor. It's also available as Snapseed as an Android app.