What are the best tools for creating quick polls that have signups and notifications (focus group tool)?

its important that i can gather a group of people with a clean and simple signup form and then ping them everytime i need something answered. I should not have to create one poll and then email it to 500 people.

its important that i can gather a group of people with a clean and simple signup form and then ping them everytime i need something answered. I should not have to create one poll and then email it to 500 people.