My number one go-to hair style is the Orchid bun, it is secure all day and looks radically different depending on the specific way I pin it or what hair accessories I use. It can be secured with pins (generally I use Goody Spin Pins for this), hair forks, or giant clips like Ficcares or flexi-8s. My hair is only just long enough for this style.
If I have more than a minute, but less than two, I do a flipped braid. For this style, just braid hair down the center, fold the ends towards your head, then fold at least once more and secure. This can be done with much shorter hair, and indeed my hair is getting a bit long for it, as I have to fold it over 3-4 times. It can be secured with a big clip or barrette of some kind or a hair stick.
With a little more time I will do a figure-8 or Infifity knot, usually the figure-8 though as for some reason it seems to be more secure on my head. The best tutorial for these ever is here. I usually use Amish pins to secure this, one piercing and attaching the top coil, and the other going from the tucked in end up. The top one can be replaced with a hair fork or stick. This is another which my hair is just long enough for.
If I am feeling slightly more fancy and not wearing a necklace with a particularly tangle-y clasp I like this style, inspired by one worn by Yvaine in the Stardust movie. To make this, roll the hair along both sides of your head and gather into a low ponytail, pull through elastic twice, then only pull through half way, creating a loop-bun with a length of hair outside the loop. Twist the length of this hair, then coil around the ponytail and secure either with pins or a hair comb. For shorter hair, leave the bottom section of hair outside the ponytail then twist and coil that.
For extra fanciness I will do a crossed bun. For this, divide the top and bottom sections of your hair, twist the top and make it into an infinity bun, then twist the bottom half into a figure-8 bun, pulling the top coil over the middle of the previously made infinity bun. To secure, I use 3-in long Amish pins, on in through each bun. This is a particularly messy version, usually it looks more elegant.
If I have actual time I will do heidi braids, which are not in the video because they take awhile, but I think everyone knows them. Braid hair into pigtails, cross on the top of the head and pin. They tend to work best if your hair is long enough that the braid over lap by at least 2 inches on the top of your head.
Here is the instructional video, featuring my latest musical discovery the German Electro-Medieval (best combination ever) band Helium Vola, and played in double-time (no meth was used in the creation of this video)