The limits that are the most likely to concern you are as follows:

• The maximum size allowed for your CloudFormation template is 50 KB. This is quite generous, and if you hit this limit, you almost certainly need to think about breaking up your template into a series of smaller ones. If you absolutely need to exceed the 50 KB limit, then the most common approach is to upload your template to S3 and then provide an S3 URL to CloudFormation to execute.
• The maximum number of parameters you can specify is 60. If you need more than this then, again, consider whether or not you need to add more layers to your cake. Otherwise, lists or mappings might get you out of trouble here.
• Outputs are also limited to 60. If you've hit this limit, it's probably time to resort to a series of smaller templates.
• Resources are limited to 200. The same rules apply here as they do for the previous limit.
• By default, you're limited to a total of 200 CloudFormation stacks. You can have this limit increased simply by contacting AWS.