There are many MANY places to watch it online, but depending on where you are in the world and what programs you have installed on your computer (Adobe flash, DivX etc.) some will and won't work for you. What I would recommend would be to go to sidereel and click on the episode you want to watch. It will come up with a list of different sites (not all will be free but just go back a page if they try to make you pay or do surveys etc.) and find out which one works best for you.
there is a site called yidio.com
go there and search up true blood to get to the main page
if u go there then they give you links to places u can watch all the episodes from season one and season two
or try this link link
letmewatchthis.ch and go on tv shows, then search true blood and it gives you all the episodes ..click the episode you want and it has greaat links :D they usually have megavideo.. thats your best pick :) hope i helped :)
The best place I've found is HBO Go (www.hbogo.com). The only catch there is you must be an HBO subscriber to sign up for it. If you are an HBO subscriber - it's totally free to use via your computer or even mobile devices that can connect to the internet (i.e. call phone/iPhone, iPod Touch, etc..).
You can go to either vodly.to or solarmovies.so. Just click tv shows, type in true blood, and it will give you a bunch of links to watch it from. I recommend using the putlocker or sockshare links. You can also watch other tv shows and movies here.
for example, if you want to watch season six episode 1, then you type into your search engine "megashare true blood season 6 episode 1". it will come up on the first one for 'web'.
if you have OSX software, then you'll probably need to download Genio. it will allow you to stream videos through your computer. if you don't have OSX software but windows software, you'll have more choices for free watching on the internet.
megashare isn't the best quality, but i get desperate because i don't have windows software. i usually buy the season to watch it, but i don't want to wait a year to get watch it. i only do that because i can't watch it on tv.