I tend to do a lot of ranting on my tumblr It's great because even if I'm too lazy to type it all, there's usually a GIF to reblog that says it all.
Also, I find that a walk is sometimes good. Sounds weird, I know and once upon a time, if somebody said that to me, I would be like "..." but honestly, it's not so bad. Sometimes, I'll get my dog and near where I live, there's a big hill with a field and some lodges. I'll walk up there and sit in between the lodges and it's so pretty, I just like staring at the water and it gives me time to think.
Other times, I've been known to hop on a bus and go to the animal shelter. They know me by now so if I'm in that mood, I'll go in, get a dog and go for a wander and that usually calms me down. Mostly because I make myself because I think "If I'm going to be your only walk of the day, you're not going to have to deal with me being grumpy!" and I'll talk to the dog and what not :L And when I come back, one of the staff or other walkers are usually around and if I'm still a bit, erm, emotional or peeved, it's not long before I have to hold a conversation or somebody cheers me up
Art's also good. Especially painting! I never really keep anything I paint but just having an overall idea and just using the brush to swish about is great and I can lose myself for hours - it's a great outlet.