Behr paint is the old Home Depot stand-by. It's the Home Depot version of Valspar (see below). For years considered a sub-standard paint, Behr has expanded its product line to include premium and eco-friendly paints.
So, here's the trivia about Benjamin Moore. They do not brand-out; they do not supply on "exclusive contract" to retailers. If you want Benjamin Moore paint, you go to a brick-and-mortar Benjamin Moore store. As such, it's a very total, wraparound experience to visit a Benjamin Moore store--nothing else there to distract you, as there might be when shopping for Behr at The Home Depot. I like Benjamin Moore, and it's nice to talk to a staff knowledgable about paint.
Devoe Paint--cool, innovative, and oh...the oldest paint brand in North America, dating back to 1754. Devoe Paint is one of those boutique, independent paint companies; it's hard to find, but well worth it. Don't bother with the website: it's difficult to navigate, uninformative, and the pictures are tiny. Dangit. I'll keep my eyes on this one and let you know if things improve...
Update 2013: Two years after I wrote this article, Devoe's site, with its tiny photos and difficult navigation, offers few rewards for anyone looking for inspirational room scenes.
Fuller O'Brien is the wild card; I know little about it and have heard no DIYer ever use it. My educated guess is that it's mainly used by contractors. I keep logging into the Fuller O'Brien site every few months for improvements, but it has little to offer. Check elsewhere for paint design ideas.
More attuned to the needs of contractors, Pratt & Lambert doesn't show on most DIY painters' radar screens. On their site, you can find only the most basic information about this paint company--but not much more. It's hardly worth a glance.
Ralph Lauren Paint and their site are my favorites. The paint is always fresh and innovative, and the site perfectly displays this range of innovation. Be sure to check out Ralph Lauren Paint, even if you think it is beyond your price range.