NHL Gamecenter
NBA League Pass
NFL Sunday Ticket (currently DirecTV exclusive via contract)
* I am assuming you are American and/or care only about the four major sports in the US. Not sure about futball, rugby, cricket, tennis, cycling, etc
Honestly, I bought a TV antennae from best buy and a long HDMI cord for my laptop and that's satisfied all of my sports needs through OTA broadcasts and questionable streaming sites.
It's almost bad enough to make me want to pay for cable. Almost.
Unfortunately for me, I live in Canada, where OTA stations do not care about the NBA. And I refuse to buy the League Pass since any games broadcast on cable would be blacked out.
In California, I can catch most of Detroit's games. In a major hockey market like Toronto, however, Detroit's games are often on TSN2 (think ESPN2), which means they are blacked out. Cable was the only way to see these, even though I would have guessed they were out of market.
As for the merger, I hate it because I actually think DirecTV is a pretty good product - even though the price is a bit high. I don't think a merger will do anything but reduce the quality of service, increase the price or both!
Don't worry - once your ISP is able to charge each streaming service more money, they might be able to budget to upgrade to slightly faster service a few years later.
$20 per month, all games streamed in HD plus your choice of broadcast options (ie- home / away feed on NBC or TSN, etc).