I always go on these:
link (this site's great for speedy updates, but it's been known to lag and have formatting issues; however, it's also great for finding new Anime to watch -- my first choice for finding new series)
link (I Amore this site because, it doesn't have just episodes for streaming, but downloading too. An AMV maker's absolute best friend! Also, this site's not too bad on speedy aggiornamenti too)
link (this is the site te go to when te JUST CAN'T find the series online. The selection of series on this site is so amazing! Problem is the pop-ups and ads, but if te get passed it, te have a perfect fonte of online anime)
To a lesser extent, there is also:
link link and, when all else fails, I go to a Google video search, but it'll probably give te the same links I gave you.
^_^ I hope that helped~!