You may have to set OneDrive to automatically download your camera backup folder to your PC itself. By default, OneDrive folders are viewable on the desktop but aren't actually downloaded to your hard drive in Windows 8.1. To learn how to change this see "How to force SkyDrive to store your files on your hard drive in Windows 8.1."
Google+ (Android, iOS)
Rumors about its expected demise aside, with Google+ all your photos can be automatically uploaded to the search giant's social network, but they're stored privately and not shared with others by default.
Unlike Dropbox and OneDrive, using Google's solution won't get them on your hard drive automatically. Nevertheless, once your photos are in Google's cloud, downloading them onto your hard drive takes just a few clicks.
Open Settings > Auto Backup inside the Google+ Android app to start saving your pics to Google's cloud. For iOS, follow Google's instructions here.
Don't like the idea of automatic uploads, but still hate bothering with direct USB connections? AirDroid can connect your PC and phone without a single wire. Once connected, AirDroid lets you easily shuffle files back and forth between your smartphone and PC. Check out our previous AirDroid primer for a tutorial on how to use this must-have Android app.
BitTorrent Sync Beta (Android, iOS, Windows Phone)
This one's for people who love automatic backup, but hate the cloud. BitTorrent Sync uses peer-to-peer filesharing to send files from your smartphone to your PC, with no third-party server standing in the middle. BitTorrent Sync requires you to have an app installed on your PC as well as your smartphone.
Once that's done, add your pictures folder (such as /storage/sdcard/DCIM/Camera) to the Android app and BT Sync will generate a secret code for the folder. Then just share the folder's secret code with BT Sync on your PC and watch the magic happen.
On iOS, just tap Backup > Backup Camera Roll, email the secret to yourself, put it into BT Sync on your PC and you're done.