I would not buy the mixed bag of capacitors.  Unless you are just going to experiment with electronics in the future.

What I used  is a 6.3 volt, 10 microfarad  capacitor, polarized Electrolytic (a 25V version works too!)  Make sure it is polarized.   I don't think a non-polarized version will work with the 555.

You can look up digikey and Jameco electronics they will sell you individual parts or a bag of parts.

I think this is the power supply you mentioned:

http://www.amazon.com/Mastech-HY1803D-VARIABLE-POWER-SUPPLY/dp/B000CSQK5E/ref=sr_1_1?s=electronics&ie=UTF8&qid=1338401380&sr=1-1

I had this discussion with ModelmanTom and he purchased this power supply.   The last I heard from him is that he loved it.   The reviews look good as well.

I would stay away from dirt cheap power supplies.   They will not hold their voltage and will not be accurate.

I bought a really old one off of ebay for about the same amount of cash.  It is old but still works very well and is probably more accurate than my mulitmeter.

Hope this helps!

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