Nice one, the other knot was new. Instead of rapidshare I use
http://www.mediafire.com for the last couple of years. They don't bother me if a file is not used for a long time, I have private folders too, no captcha code to enter and no waiting time, just click and download. Also programs like img2pdf, acrobat professional, etc. make pdfs, just number the images 001.jpg, 002.jpg ... in order.
You can try out knots with a piece of rope or cord on the sofa and use your knee(s) as a stump. It's fun. Tip: to secure most knots ending with a bow tie: pass the end of the line through the final bow.
The 2nd knot Ray uses below is a secured version of the Siberian Hitch and the last is yet another version of the many Trucker's Hitch variations which is one of the most useful.
http://www.youtube.com/watch?v=KE7dx0WJo9o
Siberian Hitch:
http://www.youtube.com/watch?v=h4T0IUjsDs8
A good version of Trucker's Hitch suitable for variable tensioning:
http://www.youtube.com/watch?v=ywqx_3TLSd8
For hammocks Trucker's variations, secured ones with extra bow tie and/or through the last loop, are good. For tensioning tarps/tents: if you don't want knots, take a piece of hard plastic like the white piece below in the picture I uploaded. It can be straight like the metal one. Cut 3 holes in it. Pass the line through all 3 holes & make a loop. The bigger the loop the shorter the overall line. Tie a knot at the end of the line so it doesn't slip out. Pass the end of the line under the cord between the 2 holes (picture below: line between the top 2 holes, not seen & facing the board) and tighten. You can pass it under twice or tie a bow tie to make sure. You can also make them in camp with a knife and short pieces of hardy wood, smooth out the holes so the line is not damaged.