Another vote for MailShot. It works with your existing Contacts list and allows you to create a special type of 'MailShot' Group, which appears as a single entry in your Contacts list.
So, for example, if you established a MailShot Group called 'Family', you could add 'Mom', 'Dad', 'Sister', 'Brother' from your existing Contacts list.
MailShot puts a special entry into your Contacts list called 'Family'. It highlights it with a special icon so that, when you're scrolling through your Contacts, you can easily distinguish this MailShot 'Group' from other Contacts, because it appears in your Contacts list just like any other contact.
Now, when you come to send an email using, say, the iPad's native 'Mail' app, you just type (or start to type) 'Family' in the 'To' field. If 'autocomplete' is enabled, then 'Family' will pop up as a suggestion. Accept it and it's entered into the 'To' field as though it were a single address. But, cleverly, it contains all the addresses that you've associated with 'Family' - i.e. 'Mom', 'Dad', 'Sister' and 'Brother'.
Type the email, hit send and it's away to all those members. Better still, look in your 'Sent' mail and you'll see that the 'To' address has been 'expanded' and it now shows the individual members that you've sent to.
What's 'special' about MailShot is that it works with existing iPad apps. Other third-party apps that handle groups need to use a special email client. This is especially useful if you want to email from other apps - say sending a web link from Safari, or emailing a PDF from iBooks or a document from Apple's Pages app. All of these in-app emails use the iPad's default email client - the iPad 'Mail' app. So being able to specify a group in the default mail client can be a big plus in these circumstances.
The developers of MailShot (I have absolutely no connection with the company) are also very responsive to user suggestions for improvements and enhancements. For example, there's a discussion going on at the moment as to whether MailShot should offer the facility to order group members alphabetically or not - with some wanting that facility and others not!
Definitely recommended if you use the iPad for Group mailing.
Tim
Scotland