The Greatest Albums of All Time?

I have decided to start a personal journey, one where I will list the seven greatest albums of all time. There's only one rule: the album has to be on my iPod, which just so happens to be a 30 gig and is practically full (I think I have just under 1 gig of free space left to occupy). This journey will take some time to complete, but will hopefully yield a better understanding of what's in my library and what needs to be out of my library. This challenge will be difficult, as it will span many genres, but also leave out others.

I will base my decision on lyrics, the music, and whether or not I like the combination of the two, which I should, since they are on my iPod.

Once I have listened to and decided, I will post the results here. Until then, faithful readers, I have a challenge for you: what do you think the best albums of all time are? And, more importantly, will they be on my iPod? I have music ranging from the 20s to now, mind you, and in many different genres, except rap and hip-hop. Does that imply that I have polka music? Yes. Does that also imply that I have some yodeling? Again, yes. What about country. Aye. Classic rock? Of course. Gospel? Yep. Death metal? Um, no, no death metal either. The hardest stuff on there is System of a Down, Linkin Park, and Flogging Molly, I think. I think I have a pretty good feel for what's on my iPod, but I fully expect to be surprised, too.

Anyway, what are your favorite albums?
[Disclaimer: Your albums will not affect my decision on the best albums. Take it or leave it.]