I think there's enough interest for a betting thread. Now I won't have to sift through pages of debating the finer points of Trump's racism to find out what 2+2 thinks of his chances to win South Dakota.

The two main betting sites that have been getting chatter on 2+2 are Predictit and betfair. As an American I only know about Predictit.
Pros:
The interface is nice and the betting is similar to intrade(really miss intrade). They will let you fund your account with an American credit card.
They have pretty liquid markets across a number of different bets. (like who will place 3rd in a state)
Cons:
One major downside is a 5% cashout fee.
Another downside is a 10% winnings fee, but that's not too bad because it's only on your winnings. If you make a $100 bet and win $0.10, you pay $0.01 unlike sports betting where the whole bet is taxed.
There is an $850 limit per contract.
The website is very slow on election days. Don't assume you can easily cashout a falling position during election result reporting. I hope they buy some new servers with their heavy fees for the upcoming general election.
Workarounds:
To avoid the 5% cashout fee you could play several 98-99c markets in a row to make 5% before cashing out. Sometimes after an outcome is decided bettors want to cash out their winnings at 99c to avoid waiting on predictit to assign the winner.
You can sometimes workaround the $850 contract limit by making the same bet multiple ways. Take Hillary to win the election and take the "next president is female" position.

Free money:
Right now on predicitit you can buy Hillary to win at 48c and buy "next prez is not female" for 44c. That's 92c for a $1. But like I said, if that's your only bet predictit will take 1c for the win and 5c for the cashout.
You're welcome.