This set of components will give good results for a 100 foot Audio loop, which is enough to accommodate about 30 people in a typical meeting room.


Power Amplifier
Radio Shack 40 W Public Address Amplifier 32-2002
  129.99
Loop Cable
100 feet, 4 conductor, 20 gauge, stranded, non-shielded
Mouser catalog #  602-1896/4C-100
    25.97
Connectors
Four position trailer wiring - Hoppy 48245, available at Walmart
     9.97
Microphones (2)
Radio Shack # 33-3021  
   39.98*
Microphone cables (2)
RS catalog # 42-2378
     9.98
Carrying Case  
I found an aluminum "briefcase style" at Lowe's.
    25.00
Total Cost:  
$240.89

* These mikes are sometimes on sale for about $10 each, and the PA amp is sometimes on sale.
The PA amplifier specified above has two input jacks for 1/4" microphone plugs and the amp does not supply phantom power. Therefore, microphones must be the dynamic type with a 1/4" plug or electret microphones, such as lapel mics, can be used if they contain their own battery. Small electret mics usually have a 1/8 " plug, so an adapter must be used for the 1/4 " jacks. The amp also has an "aux" input with an RCA type jack. Patch cables used on VCR and TV equipment fit this kind of jack, and a TV, VCR, or DVD player can be used as an input source.