A Multitude of AppsI know the apple-verse is overwhelmed with solutions here, but I’m dragging my feet joining the party. Clearly instagram is the most popular but the apple store is awash with photographic apps. I’m more familiar with the android market, and google play also have plenty to choose from. If up have an android phone I suggest you check out Aviary, Snapseed, Pixlr Express, and/or Photoshop Express all free to download. I also love HDR Camera+, which does the processing and sharing “inphone” (no computer or other software required)
My USB Digital DarkroomI have been carry around a universal card reader and USB key with some photo portable apps in my camera bag or a while now and they have been real life savers on several occasions. These do need a cyber cafe;s computer or your laptop to connect into but you can get very close tom if not as good as, photoshop and lightroom level work with portable apps like Gimp Portable & Raw Therapee Portable just from an application that doesn’t need to be installed!
On-line Photo EditorsThere are now many places that let you perform decent post processing on full size images from a web browser, so you probably want to have your netbook or laptop connected. I personally like Aviary for Google Drive (a chrome app) but Pixlr is damn good as well.
There is really no reason why you can’t take a great photo, then collect your thoughts over a coffee while you tweak it into being a true masterpiece and have it published on-line before you leave the cafe. However please use this new power wisely don’t choke the available bandwidth with copycat blandness or fill the social end of cyberspace with banality and imitative junk.