Useful English System conversions/units:
I would like to apologize for these in advance... but I can't.  If you have others that you would like to add, email me your contributions.

Length & Distance

Half of a large intestine 1 semicolon
Ratio of an igloo's circumference to its diameter Eskimo Pi
2.4 statute miles of intravenous surgical tubing at Yale University Hospital 1 I.V. League
16.5 feet in the Twilight Zone 1 Rod Serling
Given the old adage "a journey of a thousand miles begins with a single step," the first step of a one-mile journey 1 Milliwalkee
Time it takes to sail 220 yards at 1 nautical mile per hour Knot-furlong
Shortest distance between two jokes A straight line

Quantity of Matter, Mass, & Weight

6.02 x 1023 avocados
(This is, of course, Avocado's Number)
1 guacamole
2000 pounds of Chinese soup won ton
453.6 graham crackers 1 pound cake
1 kilogram of falling figs 1 Fig Newton
1000 grams of wet socks 1 literhosen
Mass which an evangelist carries with God 1 billigram

Time & Space (including units of velocity & speed)

Same great 365.25 days but  half the calories 1 lite year
Speed of a tortoise breaking the sound barrier Mach Turtle
Time between slipping on a peel and smacking the pavement bananosecond

Light & Sound

1000 aches 1 megahurts
1 millionth mouthwash 1 microscope
1 million bicycles 2 megacycles
106 phones 1 megaphone 
10-6 phones 1 microphone 

Biology and Medicine

Basic unit of laryngitis hoarsepower
10 millipedes 1 centipede
10-15 bismols 1 femto-bismol
1 boo2 1 boo boo 
2000 mockingbirds 2 kilomockingbirds
1012 bulls 1 terabull 
10-9 goats 1 nanogoat 
1 millionth of a fish 1 microfiche
10-2 pedes 1 centipede 
1012 pins 1 terapin 
2 egorics 1 pairegoric 
10-3 king machines 1 milliking machine

Architecture, Construction & Home Improvement

A Half-Bath 1 demijohn
2 wharves 1 paradox
10 rations 1 decoration
10-1 mates 1 decimate 
2 monograms 1 diagram

Sociology, Psychology, & Education Theory

109 los 1 gigalo 
1015  picolos 1 gigolo
3 1/3 tridents 1 decadent
1015 files 1 petafile 
10 monologs 5 dialogs
5 dialogs 1 decalog
10-2 mentals 1 centimental 
 A face that could launch one ship 1 millihelen
8 nickels 2 paradigms

Miscellaneous Conversions

10-12 boos 1 picoboo 
100 rations 1 C-ration
2 spotted cubes 1 paradice
10-18 boys 1 attoboy 
Barney 10100   Barney googol 
10 cards 1 decacards
100 Senators Not 1 decision

From:  A very wide variety of sources.  Thanks to all contributors!