Humorous units of measurement

The best known is probably the millihelen:

Helen of Troy (from the Iliad) is widely known as "the face that launched a thousand ships". Thus, 1 millihelen is the amount of beauty needed to launch a single ship...

The beard-second is a unit of length inspired by the light-year, but used for extremely short distances such as those in nuclear physics. The beard-second is defined as the length an average beard grows in one second. Kemp Bennet Kolb defines the distance as exactly 100 Ångströms...

The smoot is a unit of length, defined as the height of Oliver R. Smoot — who, fittingly, was later the president of the ISO. The unit is used to measure the length of the Harvard Bridge. Canonically, and originally, in 1958 when Smoot was... at MIT, the bridge was measured to be 364.4 smoots, plus or minus one ear, using Mr. Smoot himself as a ruler. At the time, Smoot was 5 feet, 7 inches, or 170 cm, tall. Google Earth and Google Calculator includes the smoot as a unit of measurement...

[The sheppey is]a measure of distance equal to about 7/8 of a mile (1.4 km), defined as the closest distance at which sheep remain picturesque...

The Friedman is approximately six months, specifically six months in the future, and named after columnist Thomas Friedman who repeatedly used the span in reference to when a determination of Iraq's future could be surmised...

A 'Fonzie' is about the amount of coolness inherent in the Happy Days character Fonzie...

[The Warhol] represents, naturally, fifteen minutes of fame... 1 kilowarhol — famous for 15,000 minutes, or 10.42 days. A sort of metric "nine day wonder"...

Additional examples at the Wikipedia link.