Your poor puppy....
I am in the process of socializing my dog. I am a little late in the socialization of my dog being around other dogs. I have a 1 year old dashchund. Although she is comfortable with my parents dogs and cousins dogs. She is not comfortable with any other kinds of dogs. I am trying to do things that are inexpensive and easy to do first, and see how it works. I am taking April (my doxie) to the park every chance I have. Most of the times they have some dogs there. A lot of times, I sit there and just April look around and sniff the air and just observe everyone else.
The other thing I do is I take my dog to a dog park. They are usually free and you tons of dogs go with their owners. Basically, a dog park allows you to take your dog off its leash and run around with other dogs. But, because April is not use to other dogs, I keep her on the outside of the dog park pens that they have fenced in, but in view of all the other dogs. Slowly we walk up to the area where the dogs are. I will allow her go to into the actual dog pen. But, that is not until she stops being so scared.
Maybe that would help. I know it is hard to socialize the dog after an experience you have had with yours. I had one simialiar, which is why it is so hard. I wish you luck with it. Let us know how well your dog does.