We have touches on preparing speeches and links on writing invitation cards. Now it is time to say thank you to your guests. Here are some examples:
Thank you very much for your thoughtful gift. We really appreciate your thoughtful/personal/generous/touching/wonderful gift. YY and I look forward to using it on holidays and special ocassions in our lifes.
We're glad that you were able to join us/We are so grateful for your gift/presence on our special day, and hope you had a good time. We look forward to seeing you again this summer. Again, thanks for your thoughtfulness.
YY & ZZ
For cheque or cash:
Thank you so much for your generousity. YY and I are saving towards our new house (hoildays, furnitures, babies), and have added your gift to our special account.
(continue the same ending as above)
If the above is not helpful enough, visit http://www.themorningnews.org/archives/how_to/how_to_write_a_thankyou_note.php. It has a great article and examples on how to write a thank you note.