Hooked On Driving is the organization I like best so far. Great management, attracts a great crowd of people, driver debriefing meetings between sessions, good driving habits on the track, end of day cook outs, bands and fireworks at multiday events, free camping in the paddock, etc. An all around great time. I'll be doing their 4th of July event at Watkins Glen again next year.
MassTuning in the northeast is along the lines of OnGrid. Cheaper track fees and lax on things. Self select your run group and wider range of skill level in the groups. Sometimes a little laxness can be a appreciated, but sometimes it can lead to trouble. They have events at Monticello in NY, which is a rare to see track day events at that private club. Overall another good time.
ChinTrackDays - From what I've heard, amongst the crowd they attract are some very good drivers and people with higher end cars. I will NEVER be able to drive with them as they are far to strict. It doesn't matter that a person has "X" number of track days and currenty in the advanced group with HOD and MassTuning. First time with Chin you go to A-novice group with an instructor in the car. And you'll be there for a few days, then you get promoted to A-solo and waste a few more days continuing to drive with the newbies. The internet is littered with stories of people complaining about not being able to advance and switching to other organizations. Work your way up to the advanced group and then try going to another track for the first time. I'm not talking about your first time at a given track, just your first time there with Chin. You go back to the A-novice group with an instructor and have to work your way back up at every single track. Instructors don't have the authority to promote you. They approve you for a "check out" ride with a different person in their program. Not for me!