bugsonglass said:

I would skip Led Zeppelin I altogether.  They were still very much in search of identity.  It mostly consists of stolen blues riffs but like you say kind of jammed up and slightly countrified.  

II has "whole lotta love" which you can't have escaped if you tried.  Also few other decent songs like Heartbreaker and Ramble On.  But it's not a classic.

III is the first album they started finding more of an identity I think.  Immigrant Song is great (and you've probably heard it).  Also good are Since I've Been Loving You and Gallows Pole.

IV is arguably their first classic album and it contains Stairway to Heaven.  I could name hightlights but it's a really consistent album on the whole.  Definitely start with this.

Houses of the Holy is considered another classic.  Especially "side A" with The Song Remains the Same etc.  Probably won't grab you instantly the way IV will but it's the best one after that (out of the first five ones).

Physical Graffiti is also really good, and then you don't need to bother at all with the final two albums

Thanks Bugsie, I will take your advice.