If you're like a lot of people, you either don't have the money for a fancy loom or you don't want to wait for your loom to arrive, and you want to get started weaving, or you're using these things as an excuse for not weaving today. You have just run out of excuses!
There are things you can do. Anything can be a loom as long as you can stretch warp threads tightly between 2 points.
One is called Back Strap weaving. All you have to do is stretch some warps between you and something else.
Another is called a frame loom, you can use a large picture frame to stretch the warps on.
Another is card/tablet weaving where the warps are often stretched between 2 vertical posts. Cards/Tablets are used to create the sheds. Cards can be made from playing cards, cereal boxes, plastic place mats, etc.
Whether it's a frame or back strap loom that you decide to use to hold the warps, the sheds (the mechanism for weaving) can be created in many numbers of ways. You can construct a rigid heddle out of popsicle sticks (or even an index card) or use string heddles and a shed rod. Rigid heddle, when used as the beater, will give you a balanced weave, if you use the shuttle (or a ruler) as the beater (with or without the rigid heddle), you get a warp faced weave (just like an inkle loom). If you want weft faced weaving (like with tapestry and blankets) then use a weft yarn fatter than your warp yarns.
Here's some links to get you started right away!
Index Cards: http://www.youtube.com/watch?v=tJlaxase0F0
Rigid Heddle/Back Strap: http://bobscrafts.com/bobstuff/backstrp.htm
Laverne Waddington Back Strap Basics: http://www.weavezine.com/content/backstrap-basics (take note of the household items used to make this loom http://www.weavezine.com/sites/default/files/images/2009/wk_38_LaverneWaddington//wz_2009w38_LaverneWaddington_03.jpg )
If you want to get a little fancier, you can make string heddles, suspended them between 2 sticks (round or square, doesn't matter) and use that the same way you'd use a rigid heddle or make any number of these to create "shafts" (just like a fancy floor loom). You can suspend these "shafts" from an overhead rod to make a counter-balance loom. Just tie string to the bottom of the shafts and use your feet to change the sheds.
Here's a "backstrap loom" with a rigid heddle made from Shrinky Dinks:
You can put string heddles on a frame and use it just like you would a rigid heddle: http://www.youtube.com/watch?v=u9orgl9rW_8
How to make string heddles:
What's your excuse now?!