Yes, I spent hours searching for free best man speeches on the internet - unfortunately most of the wedding speeches I found were carbon copies of all the previous ones I found! They lacked originality and I wasn't able to adapt any to suit my own circumstances. I did find one or two good jokes, but that was about it. Anyway, these were just my own experiences, you may fair better!
Luckily I did find something worthwhile on the internet - Dan Steven's best man speeches . There was a small fee at the time (perhaps 19 dollars, might be more now?) which I gladly paid, I had a brief look at which best man speech would best suit my style and circumstances. I copied most of it (ahem) added some of their free jokes (and 1 or 2 I had in ammunition) and added some personal facts.
The whole process was very quick, I had the speech done within 45 minutes, plus it was original, funny and sincere. For the ease and peace of mind, it was the best thing I could have done.
I didn't memorize my best man speech, I wrote the main points down on cards (cards are better than paper - people can see shaky paper!) The audience laughed a lot, the speech came across as very professional, and most were quite surprised, given my slightly unreliable reputation - ahem (quite undeserved)!
As for the nerves , I used the free "Audio confidence booster"; and I used many jokes from the book that came with as well. Anyway, I hope that helps with your search for free best man speeches.
All the best, and I hope it works out for you.