As Valentin has mentioned a multimeter tester is a must. Depending on how serious you are as a hobbyist, there are lots of test instrument that you can build like an inductance tester, transistor beta tester, diode tester and many more.
Thanks Todd, this sounds good specially the low end scope. Had search for the tektronix basic oscilloscopes and as a hobbyst, amateur electronist, price is reasonable for me.
You should consider buying a reconditioned one given that they also include the "lifetime" warranty (which is really 10 years). You can search here: http://www.tek.com/buy/used/tektronix
