Mike’s Electric Stuff is a great site for browsing interesting topics related to electronics. The site covers a variety of topics and your bound to learn something new. Here are a few of the topics:

– The first ever integrated circuit from 1926!
– High-frequency valves plus klystrons & magnetrons.
– Spark gap and triggered gap tubes and small thyratrons.
– The smallest CRT you’ll ever see.
– Mercury Arc Rectifiers
– How you made DC before silicon
– Neon lamps and neon strobe tubes.
– Geissler tubes
– Geiger tubes
– Nixie tubes
– Tesla coil pictures
– Fun with Argon
– Surge generator Can-crushing
– Jacob’s Ladders
– Tesla Coil
– Neodymium magnets
– Laser power supply from surplus switchmode PSUs
– Build a cheap capacitance box
– Violet laser diode fun