Cardiff Red
Because of the food colouring used in a lot of blood recipies they tend to stain easily and can sometime look more purple than red. Here's a more natural alternative that's closer to a Spaghetti Western style arterial red. It also washes out of clothes easily and can be eaten reasonably safely (although why you'd want to eat it is beyond me).
Take a teaspoon or two of Arrowroot (a white powder used in baking that you can easily find in health food shops) and add to water heated on the stove. Stir continuously until the mixture becomes gloopy. Add a small amount of red children's non-toxic powder paint and stir in. The mixture should now be bright red. Add a tiny amount of brown powder paint or coffee concentrate (make this by adding a small amount of water to coffee granules) to darken the blood as required. Store in a bottle or jam jar and thin by adding water to make the blood the required consistency as and when you need it. For bullet hits you need to thin the blood quite a bit to allow it to spray out.

Lo-Cost Blood
Add a few drops of red food colouring to the cheapest washing up liquid you can find. Add a drop of blue colouring or some coffee concentrate to create a more realistic colour. Produces a runny blood that has a slight tendency to foam. Great for those bucket of blood effects on the cheap. Washes off reasonably well but tastes foul if you accidently get it in your mouth.

MB2 Blood
Flour Base
1/2 to 2 level teaspoons of plain flour per cup (250ml). Mix flour into water completely (no lumps) before heating. Bring to boil then simmer for 1/2 hour. Stir frequently.
Cool before adding food color. Stir in any surface scum. Makes a good base for stage blood. Slightly slimy. Fairly low surface tension. Soaks and spreads well.
One cup batch of MB2:
* 1 oz (29ml) Red food coloring (Durkee (R) brand or equivalent)
* 1/8 teaspoon (.6ml) Green food coloring (Durkee (R) brand or equivalent)
* Add flour base described above to a total of one cup (250ml). There is no sugar and very little food in the MB2 formula so it's probably less attractive to insects. Shelf life is fairly short (days) at room temp. Does not go rank but ferments a bit and looses viscosity.
This formula will temporarily stain skin. Seems to wash out of cotton cloths OK.
Courtesy of : Murr Rhame

Cherry Red
Mix 1 cup water and 1 tablespoon flour. Bring to a boil and let boil for 3 min. Then let simmer on low for 15 min. Remove from heat and let stand around 5 min then mix in one 0.13 oz. package of black cherry (powder) kool aid mix. You will see the results right away. When I priced one packet of kool aid to the food coloring it was about a quarter of the price.
It is a little thick but a good color. Another cool part is if you do get some in your mouth or have to drink it as for a vampire movie, it tastes pretty good to.
Courtesy of : Jason Dunlap
 

Black and White blood
Hitchcock used Bosco chocolate syrup in Psycho. Any opaque chocolate syrup will do. Tastes great as well!

Jelly Blood
Microwave 3-4 bottles of glycerin then add one cube of strawberry jelly and mix until dissolved. Then add small amount of gelatine (1/5 of a packet) and then add red food colouring to desired effect. Keep stirring until mixed well. It is sligtly runny but great for that reservoir dogs look in back seat of the car. All ingredients are easily found in supermarkets.