I'm working on an anthropomorphic giant octopus character (yes that's a real race, you can find it in Savage Species and it's awesome). From the two racial hit dice I get skill points equal to (2+Int)x5, but I can't figure out what the heck are class skills for animals (anthropomorphic animals use the same class skills as their regular animal counterparts). I have a vague memory that any skill listed in their entry is a class skill for them, but haven't found anything to back that up.
The Monster Manual on Skills says, "All listed skills [in a monster's stat block] are class skills, unless the creature has a character class (noted in the entry)" (7).
Thus an anthropomorphic giant octopus (Savage Species 216) has the class skills Escape Artist, Hide, Listen, Spot, and Swim, the same class skills as a giant octopus (MM 276-7).
Keep in mind that an anthropomorphic giant octopus's ECL 2 is rarely worth it, despite the awesomeness of an anthropomorphic giant octopus PC.
All skills listed in an entry are class skills
The "Reading the Monster Entries" section of the SRD states (emphasis mine):
This line gives the creature’s skills, along with each skill’s modifier (including adjustments for ability scores, armor check penalties, and any bonuses from feats or racial traits). All listed skills are class skills, unless the creature has a character class (noted in the entry). A creature’s type and Intelligence score determine the number of skill points it has.
Racial/"type" hit dice don't have class skill lists. Any skill taken with those points is considered a class skill for those HD and grants a full rank.
This is one of those things that notably changed in Pathfinder, where the skill/class skill system works a bit differently and "type" HD do have an associated "class" skill list (as can be seen on this table).