ok, some more ok-ish ideas:
1. investigating heart rate (resting) in girls and boys of similar age group.
independant variable: girl or boy
dependant variable: difference in the heart rates
this experiment will be fun and is a good one to do, but i have a limited access to guys!!! how sad is that?!!! i cant exactly go up to randoms on the bus (pauline, shirley :P) and ask to test their heart rate. it wont exactly be resting anyways, will it?

2. testing the effect of heat on rubber. I think i can do this by testing the elasticity of different kinds of rubber bands, before and after they have been heated. I'm not sure how i'll do this, but i' have 2 options:
a) attaching band to something sturdy e.g. a hook on a wall/dooorknob that wont move, then stretching it till it breaks, measuring the elasticity by working out how far back i had to pull the rubber band for it to break.
independent: whether the band is heated or not
dependent: how far back (how much it stretches) it takes for the band to break.
b) using a sort of weight and seeing how much it contracts/stretches when heated, probably with a hairdryer (cant think of anything else to safely heat it with without removing it)

3. finding the best place on your body to test your heart rate- pulse. i have a stetheoscope my dad might let me use :) let me ask...ok, he said i can use the crappy one. i dont think i'll do this idea. i kind of already know the answer and i dont think itll work out.
independent: parts of body i will test pulse on.
dependent: how well i can feel pulse on different parts of body

4. testing how well soil conducts electricity and whether increased salinity changes this.
independent variable: salinity in soil, just using table salt.
dependent: how well soil with different salinity levels conducts electricity

5. i found another fairly good egg one yesterday, after i shut down this computer and did a bit more research on the lenovo. cant remember what it was...