The advice below is going to sound a little reserved, I'll admit that up front.
What I mean to say is that humor in a wedding speech won't be exactly like stand up on TV.
This is not to say, however, that you can't build a funny wedding speech that sends waves of laughter through your audience.
It'll just take some thought to achieve, hopefully my tips below can help you with this.
1) Make sure to take your audience into account when forming jokes to work into your speech.
Take note of who is going to be at the wedding.
Remember, almost always there will be people of all age groups, beliefs and senses of humor at the wedding.
Whether you're the bride, best man, or any other role in the wedding, a bad joke can kill not only your speech but also the joyful atmosphere.
While it may not be possible to please everyone, do your best to form jokes that you think everyone can get or relate to.
2) Your jokes should tie into a central message.
Meaning that any of your "funny wedding speeches" shouldn't be all about jokes, but your jokes should be all about your speech.
Confused? I hope not.
All I mean by this is that your speech should have a central message or purpose, and your jokes should compliment this.
Having a theme (such as changes in the bride and groom, old memories that influenced your life, or even how you will setup a new life with your spouse) will help you move your speech along.
3) Give your speech a flow that enforces your central message in the beginning, middle and end.
Constant reminders of what you want to get across are a surefire way of making sure people walk away with that message.