Can our group sell raffle tickets online?

A general answer is that raffles are considered gambling, and gaming laws vary by state.  In states that do allow raffles, they are only allowed for charitable organizations, not for-profit companies or individuals.

In the United States online gambling (such as poker) is illegal and since raffles are gambling it would follow that online raffles would also be included in that ban.  However, I have not found a definitive answer to this question as of yet.

It is advised that anyone considering a raffle to consult with an attorney who has experience in this area.

That legal disclaimer being said, many charities do at least advertise their raffles online and have an address or contact information so people can order tickets.

For more information:

Online gambling in the United States information on Wikipedia

What are the raffle laws of each state?

Do you need to register in each state for online fundraising? from Idealware