Wow, somehow I fit all of Nazo's a-g criteria. Of all the Funimation dubs I've heard or heard of, these are the categories they break down into.
1) Close to the original:
Gunslinger Girl
Rumbling Hearts
Samurai 7
Basilisk
Fruits Basket
Ouran High School Host Club
Fullmetal Alchemist (2003)
Full Metal Panic: TSR (technically an ADV dub)
Always my Santa (some of the writing leans towards category 2, but they left quite a few Japanese words in due to Mai's "items beginning with san-" powers.)
2) Somewhat different from the original:
Shuffle
Solty Rei
Trinity Blood
Kiddy Grade (borderline category 3)
Kodocha (The first disc was category 3, but the major changes stopped after that)
Suzuka
Tenchi Muyo OVA 3 (probably, though I didn't have the subs on to compare)
3) Vary widely from the original:
Negima (2005 Xebec version)
Desert Punk (faces always covered with masks = fewer mouth flaps = lots of freedom)
Burst Angel
YuYu Hakusho
Dragon Ball Z (especially with the old version)
Blue Gender
Tenchi Muyo GXP
As others have said, dubs for comedic and/or older shows tend to be liberal, while dubs for serious and/or newer shows tend to faithful. And imo, faithfulness to the original is not the be-all, end-all for dub quality. Not all Japanese screenwriting is stellar work, so if dubbers are able to make some improvements while still fitting mouth flaps, characterizations, and the overall story, more power to them. Like with Negima '05, I found that show a lot funnier in dub than when I watched it fansubbed, due to the dialogue changes. It was ADV's Ghost Stories dub that first taught me that "different from the Japanese" was not equivalent to "worse." Fair warning, that dub's more liberal/unfaithful than anything listed above.
Generally, the reviews at AnimeNewsNetwork will comment on how faithful or unfaithful the dub is on a given DVD.
