I run my blog on a t1.micro available under aws free usage tier. I have been facing memory crunch due to only 600mb available ram. http://aws.amazon.com/free/ says that free tier provides t2.micro instances which have 1gb ram. I was wondering if its possible for me to upgrade to the same in free tier.
Yes, that should be no problem. Just stop your instance, and you can then change the instance type to t2.micro and start it again. For other instance types, you'd have to worry about losing data from your instance-store volumes, but t1.micro and t2.micro instances don't have any. However, you should note that its IP addresses will change unless you have an Elastic IP Address for it.