The bowline is perhaps one of the best known loop knots. The knot itself has the same structure as the sheet bend, but here only one rope is used. The bowline is quick to tie, easy to open and it never jams. However, it may capsize and it is quite weak, reducing the strength of the rope by approx. 50%. The bowline may also be doubled (as the sheet bend), which gains some sequrity. To do this, double the 'little' loop in the first drawing. Despite its shortcomings, the bowline (and the sheet bend) remains one of the best all around knot.
This is a very good loop, it's secure and has very good lead. Ashley mentions, that this can sometimes jam, but I've never had any problems untieing it. Whenever I need a semipermanent loop at the end of a yarn, I use this one.
Double a piece of yarn, and make a figure eight knot. The loop is strong, but a bit bulky and hard to untie, but quite handsome.
This is also a well known knot tied on the bight (no end of a rope needed). It is secure and quite easy to untie. To tie: Take three turn around your hand. Lift the innermost turn to the middle. Then take the new innermost turn, extend it, and pull it trough all the turns. Tighten the knot. You will see, that the loop has excellent lead and the loop stays perpendicular to the rope.
This is probably the best loop on the bight if the load is perpendicular to the rope. The loop is strong and extremely easy to open, even after heavy load. Just pull up to rightmost loop in the knot to loosen the whole knot.
There are many loops under the same name, but this is the one I've learned. Follow the diagrams to tie it. This has also excellent lead, but not so easy to untie after use. The loop stays parallel to the rope. Use several of these on a rope eg. as an improvised emergency ropeladder.
Sometimes one needs more than one loop at the end of the rope. The portugese bowline is a quick way to do it. Make a small turn, then to larger turns. Finaly secure the working end to the standing part by tying a 'bowline' trough the small turn. The bad new are, that the loops aren't independent, that is, you have to pull on both loops, or else on loop will pull material from the other.
The bowline on the bight is probably the best known double loop knot. It is secure and strong. The only drawback is, that the loops have to point approximately to the same direction. To tie: Double the rope, and tie an overhand knot with the doubled end. Pull the produced loop over the overhand knot. Then following the diagram, take hold of the double line and extend it, working the material from the single loop into this double loop. You may leave the short end free or bend it to the standing part with a bowline.
The spanish bowline is a beautiful double loop knot. Follow the diagrams to tie it. The last drawing shows the knot turned over (this side looks better). Work the knot tight, or some material will be pulled from one loop into the other. The pull on the loops don't have to be parallel as in the previous knot.