The thing about M&A rumors is that by the time it hits the financial press, most of the upside is already gone. Once the rumors have been confirmed, there's next to no upside, maybe 5% at best. Now, 5% for low risk is nothing to be sniffed at, but you would probably do better just throwing it in an S&P500 index fund.
MarketScreener.com
So, I was looking for sites that discuss potential M&A opportunities and they're hard to come by. One that I found was marketscreener.com.
The M&A news section is pretty hidden but you can find it under the News tab, then click on Companies and then Mergers and acquisitions. What I like about it is that it isn't hidden behind a paywall and that subscribing alone will give you access.
SeekingAlpha M&A News
Another good source for rumors and not just confirmed news is SeekingAlpha. While it is not as good as MarketScreener in my opinion, it is pretty decent. The only downside is that this is hidden behind a paywall now that seekingalpha is trying to monetize.
What is free, though, is reading headlines. So if news about a particular company catches your eye, you can read all the m&a news by filtering for a particular company.