I had a Transcend 16GB MicroSD card that just stopped working (would not mount in the phone or with a PC) and this is my story as to how I recovered my pictures and videos:
I purchased my Galaxy S3 (Verizon) in July 2012. At that time I backed up my MicroSD Card that I was using in my HTC Incredible. I used my MicroSD card for almost 4 months in my S3 and it worked just fine. Then one night there was a notification (exclamation point on the top of my phone) that the SD card was not detected. After rebooting my phone a couple times, using the MicroSD adapter, and testing the SD card on a different phone, the SD card would not mount. It was as if the SD card didn't even exist. I even had a friend at work try to get it to work using his laptop and Linux (not Windows). The computer could see that an SD card was inserted in the slot, but it was not readable.
I tried using software (PhotoRec) but since the MicroSD card couldn't be recognized, the software would not work. I researched the internet and came across Recoverfab:
fix repair CF SD SDHC memory card/flash drive-format error software
They are a professional SSD recovery firm.
I called Recoverfab and spoke to the owner, Leopold Hiersche. I explained my issue and he said to fill out the order form and additional instructions would be emailed to me. I did that and instantly received an email back with further instructions as to how to send my MicroSD card to him. I went to the US Post Office, bought a padded envelope, stuck in my MicroSD card that I taped to my folded over business card for protection, included a copy of my order confirmation page, filled out the customs form (said that the package was a broken memory card and claimed it was work $1), and mailed the package to Germany for less than $5 (envelope included). I did not pay more for it to be registered mail per the suggestion in the FAQ on the Recoverfab website.
I mailed the envelope on Wednesday and the next Tuesday (6 days later) I received an email from Recoverfab that they had received my MicroSD card and that they would have an update for me within 1 week. 24 hours after they received my MicroSD card I received an email that said they recovered 684 photos and 40 videos. I logged into their site and sure enough they provided thumbnails of 100 pictures that they recovered!! I was very relieved to say the least!
Getting this type of recovery done for less than $300 is pretty awesome. I highly recommend Recoverfab if you can no longer access your SD card and you have important pictures/videos that you would like to recover. And if you send them your SD card and they can't recover the data, you are only out the cost of shipping (~$5 via USPS) to send it to Germany. You don't have to pay for the data recovery until data has been recovered!
I learned my lesson that I should always backup my data. I am considering backup options like FolderSync, but for now I have been copying pictures to my laptop manually, and then backing up my laptop to an external HDD. I am also going to start to upload photos to either flickr or Shutterfly so I at least have a copy (lower resolution) in the cloud. I hope that this post is helpful to you!