You can go to the market and type in "sms" or "text" or "group text or sms" and you should get plenty of choices, free and paid. I personally use Handcent sms. It allows you to do the multi-check boxes or you can enter the first letters of each name and it comes up.

 

Just tell the stock app who you want to text either by typing in the phone number or grabbing one from the contact list. Once you have one in there, you will notice it puts a comma after the first one. Just tap the tp: area again and add another.

 

or if you want to send text messages to certain people all the time like jokes or work related items you could just go in to gmail and make a group in there (name it something to remember i actually just called my first one text1 then had text2, sent dirty jokes to wrong group). then just type message or forward message then click on the + sign then it gives you the option to click on friends or group at the top, chose correct group and all numbers will be filled in. send