A unique calculator with no equals button - it has two text entry fields, one where you enter an expression, the other provides a running total. You can switch between them at any time, using the result of a previous calculation in a new one.
1.7.6: Bugfix: thousands separator and decimal point should work on locales other than en_US - please provide feedback if you have troubles! Thanks, Hervé!
1.7.4: Feature: added a preference to trim off trailing zeroes, so "5.200" becomes "5.2". Thanks Josh!
1.7.3: Bugfix: setting precision to 0 will work properly.