I'm looking for a single contact, female connector that I can solder on a PCB and insert components or wires in - exactly what a prototyping breadboard is made of but I want them standalone.
You can find these on the Digikey site under "Connectors -> Rectangular, headers, receptables, female sockets". At 45¢ the SAM1213-01-ND (tin finish) is not cheap, and the gold finish SAM1211-01-ND is even more than 1 dollar. That's right, that's for a single pin. I would recommend using longer rows as much as possible, since they're much cheaper per pin.
A search on eBay with the keywords "Single 2.54 Round Female Machine Pin" yields 12 sets of 40-socket breakaway strips for under $5 with machined round sockets. However, the machined sockets are not so useful for plugging in square or flat pin components, for instance, as the receptacles are not spring-loaded.
If you are looking for something more like the sockets in a breadboard, i.e. something with positive grip on both square and circular component pins, then search for "Single 2.54 Female Pin" - they are around the same price per strip.
Two caveats on the latter type:
- When cutting out individual units for use, the adjacent socket essentially gets destroyed, as there is no breakaway indentation between them, unlike in the circular ones above.
- Do not expect the kind of engage-disengage cycle lifetimes as a good breadboard offers, because the positive grip in breadboards is typically phosphor-bronze spring material, sometimes gold-plated. The low-cost breakaway socket strips are merely tin-plates brass usually.
Hope this helps.