The VPC wizard has an option to create a public subnet and a private subnet. It creates a NAT instance to handle internet traffic for the private network. The tool does not have the option to make this instance a micro instance. Until recently you could not have a micro instance on a VPC http://aws.amazon.com/about-aws/whats-new/2012/10/18/Amazon-VPC-now-Supports-Micro-Instances/  I think it’s possible to use a micro instance as a NAT, you just have to do some manual steps to implement it.
This guide assumes you already have a VPC set up with a public and private subnet and a running NAT.
Instantiate the micro NAT
From the EC2 console. Select AMIs.
Then from the pull down menu select “Amazon Images”
Then enter “nat” in the text field and press enter.
A display of available amazon provided NAT AMIs is listed
Select the 1.1 beta 64 bit, right click and select Launch Instance.
Select T1.micro as the instance type.
Select VPC and then select the public subnet (in my case 10.0.0.0/24)
I prefer to give it a static internal IP address. I assigned 10.0.0.25 to it and click Continue.
Give it the name micro-NAT and click Continue.
Select the keypair to use and click continue
Select the security groups you want this NAT to be a part of. I selected ones that gave it port 22 and access to other machines that share the same group. Click Continue
From the VPC console select Elastic IPs and click on Allocate New Addresses
Select VPC and click Yes, Allocate
Click on Associate Address.
Select the Micro-NAT and click Yes, Associate
SSH to test that it is up
> ssh -i .ec2/pats-keypair.pem firstname.lastname@example.org
Change Source /Dest Check
From the EC2 console select the micro-NAT instance and right click and select “Change Source / Dest Check”
Click Yes, Disable
From the VPC console click on subnets then select the private subnet. Note the route table it is using, in this case rtb-7565761e
Click on Route Tables and select the route table associated with the private subnet.
Remove the route to the current NAT, click Remove
Click Yes, Delete
Enter 0.0.0.0/0 for the Destination and select the micro-NAT instance as the target and click Add.
Click Yes, Create
Test the New Micro NAT
SSH into another instance on the public subnet, in my case I have a machine running with an Elastic IP at 220.127.116.11 this instance has a keypair in my home directory
> ssh -i .ec2/pats-keypair.pem email@example.com
SSH into an instance in the private network. I have an instance running in my private network at 10.0.1.30
> ssh -i pats-keypair.pem firstname.lastname@example.org
Ping google.com from the private network
> ping google.com
And it works. As good measure stop the old NAT instance.
From the EC2 console select the old NAT and right click and select Stop
Confirm that the old small instance NAT is down then try and ping again from inside the private network and/or use apt-get or wget as a test.
 Amazon VPC now supports Micro Instance