So far, Instagram has no plans of making itself compatible for uploading pics from your PC. Instagram is a "mobile first" company, while they allow you to view photos and follow users from the web, they do not allow you to upload pics from your PC. They want to keep Instagram about "photography"via mobile devices so it doesn't get overloaded with random pics from the internet (a la tumblr).
Instagram has very quickly grown into a very popular tool to be used by bloggers, however, their "mobile first" policy leaves out those without data plans or smart phones. I'm not a regular phone user, I actually really dislike using the phone. That being said, I'm certainly not going to pay a fortune for a data plan and a $600(or something, I have not researched this number) phone that takes decent photos with access to the Android/Iphone app stores. Well, lucky for people like me, there is a workaround!
The workaround is a pain in the butt, but it sure beats spending all of that money. If you prefer to use your PC, there are a couple Android emulators out there to choose from. They're very early in development, have a lot of bugs and run pretty slowly, especially if you have an older PC. I tried out Google's android emulator for developers but I had trouble making it work.
The program I ended up using is called BlueStacks, it's free and it's in Beta. I've had a problem with it once where it was stuck eternally on the "Loading..." screen but a quick uninstall and a fresh download and re-imstall solved that issue for me.
You can download BlueStacks at http://www.bluestacks.com/, there is also a Mac friendly version available. Once you have it downloaded and opened, it will look something like this...
Yours will not have Instagram yet, you need to order that from the Android or Amazon app store. Click "App Search" and type in Instagram. You will either need to log into a google or amazon account (it's free but you still need to login). Note that this is an android emulator so you can play games on it too. :)
Once you have it installed, you can create an account and login! It will automatically hook up to your webcam, so if you want to take pics on your webcam, you can do that as well.
To upload saved photos from your PC, just open a file folder and drag the photo you want from the file folder and onto the BlueStacks window and a window will pop up asking you where you want to send the photo. Click Instagram and it will work just like Instagram on your phone (or for people like me, on other people's phones) Get your hashtags ready and start instagramming (is that how you say it? >.<)!
Note: I have found that in order to add another picture in the same session, you will have to go back to the Blue Stacks main screen and open Instagram a second time to get the "Share" window to start popping back up.
I hope this helps out more bloggers than just me! I was feeling pretty left out with all of the Instagram giveaways and I felt like I was missing out on a lot of exposure for my blog. It is a pain in the butt, but it's free and I'm happy with it.
If you get stuck anywhere along the line, don't hesitate to consult YouTube!