I think the following extensions can fulfill your requirements.
1. Countdown. This flexible at configuration Magento extension allows you to create attractive countdown timers and insert them on different pages of your Magento store, customize the view of your countdown block and specify parameter for each block. The Countdown Magento extension works with Catalog Price Rules and Shopping Cart Price Rules so that you can inform your customers when the sale will start or end.
2. Catalog Permissions is a great choice for those online merchants who want to configure the visibility of different items, product prices and even the whole categories for specified groups of customers.
3. Refer a Friend stimulates your customers to invite their friends to your store. Your customers refer their friends to your store and get a percentage or flat discount on their own purchase – while you get more customers and greater revenues!