The first thing to bear in mind is that formally, your speech is a response to the toast to the bride and groom that has just been made by the bride's father, and a proposal of a toast to the bridesmaids. So you start by thanking your new father in law, and your new mother in law, for putting on a splendid bash and letting them marry their beautiful daughter. Of course you also thank said beautiful daughter for becoming the new Mrs Boyle06. Then you thank everyone for coming. Then you thank anyone and everyone who helped to put the wedding on (ushers, best man, any other friends/family who helped). Finally you thank the bridesmaids and propose a toast to them. Then you sit down.
You actually have the easiest of the three speeches because you're not expected to reminisce, tell funny stories or get everyone laughing or crying. Feel free to be a wit if it comes naturally, but don't stress about it.
When the best man gets up, formally his
only duty is to respond to the bridesmaids' toast on their behalf. You may remind him of that but I don't imagine it'll stop him telling a few stories. Just grin and bear it, and beat him up afterwards if necessary.
EDIT
Oh, and congratulations!