I have been happy using this. You need to look for the card that suits your needs. For example, long talks, or short conversations. For short you want a no connect card, etc.
Check at Hispanic and Asian markets. They sell pay-per-minute cards that are often better deals than anything name brand. Most will deduct a chunk for the connect fee, but for longer duration calls they are good.
I use the cards from nobel.com also. They have different options, each with a different price per minute. Unless I am certain I will use all the minutes on a visit to the US, I buy the one where minutes don't expire for a year. That way I can use the minutes not used on one trip the next trip to the US.
I've been using Jupiter card for a few years. You refill the card with a minimum of $5.00
From USA to DR 3.5cents/land 8.3cents/cell.
From DR to USA its 2.7cents.
Good customer service.