I figure my earlier build-a-beast post pretty much covers it, although I'll need to remove all the house-rule stuff and only focus on what duplicates or nearly duplicates the list in the LBBs. Here's my suggested chart:
|Monster Size|| ||Base HD|
|Human-sized being or herd animal||1 HD|
|double human size||8 HD|
|triple human size||12 HD|
|X times human size||X times 4 HD|
|slightly larger||+1 HD|
|half size||-1 HD|
|lives in small groups||+1 HD|
If the final HD is 0, change it to 1-2 HD; if HD is negative, subtract number from 1-2 HD. Hit point penalties or bonuses also modify morale. If you want a low-hit point creature with no moral adjustment, make it a HD/2 or /3 creature, treating it as 0 HD for attacks.
Add a couple notes for some special monster types (oozes, undead, spirits, dragons) and I think we're pretty much set.