You just started a new electronics hobby project and - BAM!  You are stopped dead in your tracks because you don't have a key part you need.  I know your frustration - I have been there.  What you need is a well-stocked "parts bin" or "junk box" that contains all of the common parts you are likely to need.

Don't fret.  Building up that parts bin is not as expensive or as mind-numbing as you might think.  Here is my guide for building up a parts bin quickly, easily, and inexpensively.

One.  Start with some resistor and capacitor assortments and grow from there.

Get a basic selection of these elementary "passive" components you will need over and over again.  You need a reasonable selection of carbon composition resistors in the 1/4 and 1/2 watt power ratings.  You will also need some ceramic disc capacitors for small capacitance values and some larger, aluminum electrolytic capacitors for larger amounts of capacitance.  Specific suggestions:

*Assortment of 1/4 watt, 5% tolerance resistors in the "E12" series.  Example:  Ebay item 7581569452 from Nightfire Electronic Kits.

*Assortment of 1/2 watt, 5% or 10% tolerance resistors.  Example:  MCMinone.com item 80-6670.

*Assortment of small value (.1 uF or less) ceramic disc capacitors.  Example:  Ebay item 300145152931 from APM Mall Enigneering.

*Assortment of aluminum electrolytic capacitors.  Example:  Ebay item 250159127473 from Electronic Components and Parts.

Two.  You need some pots!

Not the clay kind - potentiometers.  Get an assortment of the common panel-mounted pots (both linear and audio taper) and an assortment of "trim" pots (for fine adjustment of resistance that is set once and usually left alone).  Specific suggestions:

*Check out the great assortments of pots at The Electronic Goldmine:  goldmine-elec.com.  Items G15372 and G14053 should get you started.

Three.  You need connectors!

Simple little things like not having a banana jack or DC power jack handy can be really frustrating.  Here are few suggestions for getting a basic inventory of these critters created.

*Package of banana jacks - red and black.  Example:  Set of 10 pairs at Fulleclipse - Ebay item 300110727922.

*Package of 18-22 gauge female and male quick disconnects.  Example:  Bags of 100 each at Lights and Electrical by Lien - Ebay items 4550507929 and 4550507951.

*DC power jack.  Get a couple 2.5 mm male jacks.  Jameco.com part number 151563 or similar.

*DC power plug.  Get a couple 2.5 mm female plugs.  Jameco.com part number 168242 or similar.

Four.  Can't experiment without diodes.

There are two kinds you need for your "basics" parts bin:  "Small signal" diodes and "rectifier" diodes.  Small signal diodes are low-current, "one-way" gates in circuits.  Rectifier diodes are higher-power.  These are designed to take a varying AC voltage and block the reverse parts of it (or, in a full-bridge configuration, invert the reverse parts of the AC).  Sometimes rectifier diodes are circuit protection devices, blocking an a reverse voltage that shouldn't be present.

You may also need "zener" diodes to produce specific voltages in your circuits.  Buy these individually as you need them

Specific suggestions:

*1N4002, 1 amp, 100 volts, rectifier diodes.  Here's 100 of them for $5:  Ebay item 150153649868; Ebay store APACO Electronics.

*1N5401, 3 amps, 100 volts, recitifier diodes.  Mouser.com carries these for $.16 each.  See Mouser stock number 863-1N5401G.  Get 10.

*6 amps, 400 volts, bridge rectifier (4 diodes in one package arranged as a full-bridge rectifier).  See Mouser.com., stock number 583-RS604.  Buy a couple.

*1N914 (or the equivalent 1N4148) diodes.  These are low-current, low-power diodes for signal switching in your project circuits.  Buy the 50-pack at Radio Shack (part number 276-1620) for $2.59 and you are set for years.

Five.  Get some *very* common transistors.

Nothing exotic or esoteric here.  We are talking about garden-variety, widely-available, well-known parts that electronics experiments and simple projects call for.  For example, when a project says, "any small signal, NPN transistor will work," have some 2N2222's on hand!  Here are few basic transistors I always keep in my parts drawer next to my workbench:

*2N2222 NPN Transistors.  How about 100?  See Ebay item 140151452428 from Ebay store Surplusplus.

*2N3906 PNP Transistors and 2N3904 NPN (complementary) Transistors.  How about this deal:  You get 100 of each *and* hundreds of useful diodes for a mere $25 (includes shipping from China).  Ebay item 330158107736; Ebay store Sure Electronics.

*2N3819 N-channel JFET Transistor.  Bag of 50; Ebay item number 120155625560; Ebay seller dpi4parts.

*Any N-channel power MOSFET transistor.  How about the IRF720?  You get 20 of them.  Ebay item number 120154872830.  Ebay seller dpi4parts.

Six.  Switches

You need a few basic types to bring your creations to life (and turn them off again quickly when you see smoke).

*SPST "on/off" switch.  It turns the power on.  It turns it off.  Enough said.  Ebay seller "Abeja" sells a nice, snap-in, rocker switch by Carling in lots of 40 for $9.67.  Great quality at a great price.  Stock up!

*DPDT toggle switch.  Switch two circuits on or off simultaneously.  Good old toggle switch mounts in an easy-to-create round hole.  Buy a 1/2 dozen.  Great quality switches are available from "HongKongSuperSeller" ("PartsPipe" Ebay store).

*Momentary "on" pushbutton switch (normally "open" - closes when you push it).  You need about 6 of these.  Check out the good quality and prices at RSR Electronics (elexp.com).  Try part number 17MOMR1823B for a mere $.75 each ($.60 each if you buy 10).

Seven.  Fuses and Fuse Holders