I had to open my big mouth during a brainstorming session recently at work (I know, I know, no nega-comments during these sessions) when I corrected the moderator's white-board spelling of judgment, in which he had included the e after the g. as the Brits and Aussies do.
Later, the word knowledgeable made its way to the board, so the moderator–fearful of my puritanical addiction to classic American English usage–took the e out.
At least this time, my spelling observation led to a group discussion of what to do with the e in words when you add things at the end. We resolved nothing then, but we agreed that loveable without the e just wouldn't pronounce correctly.
The brainstorming moved on from there, but later I decided to look up the rule for dropping and keeping the e. Here's what I found, as least concerning the addition of suffixes:
1) Drop the e if the suffix begins with a vowel: use+able=usable
2) Retain the e if the suffix begins with a consonant: use+full=useful (where did the second l go?)
Which brings us back to judgment. Ment starts with a consonant, so where's the e?
Maybe British English has it right after all (but of course, ment isn't necessarily a suffix).
Anyway, those two rules should hold sway most of the time. The rest of the time, just pick a different word if you're unsure of the spelling. Single syllable words always work well without a bunch of confusing rules (but you run the risk of sounding and reading like a mental midget is you just use single-syllable words).