The first 3 as AinulindaleFBS said are solid. I first read them when I was in 4th grade. I liked them back then. I still like them now. They haven't lost their luster in my eyes.
The last two, however are vasly different to the first three. Actually, what I think of the books is:
1. A Wizard of Earthsea is really good. It tells the story, Stuff happens, not very profound. Good read if you don't mind reading something superficial.
2. The Tombs of Atuan is also very good. Deals with the Ancient Ones a lot. Deeper than the first one by all means.
3. The Farthest Shore is the turning point from books one and two to four and five. Theres plenty of action that LeGuin describes well but concisely. There is also a lot of meaning in this one. Immortality and whatnot. It is still good compared to the first two, but if you like your fantasy to have a deeper meaning.
4. Tehanu is strange. I read it. I found it boring the first time around. Dropped it midway. Second time I picked it up, same thing happened. I reread it a year or so ago and this time it wasn't as bad as I thought it was earlier. There is no more magic and stuff that was in the previous books. No dragonslaying. the guy is old and tired. But there is meaning in it and I guess that I just had to mature to read this and enjoy it.
4.5. There are two or so stories that the poster twice before me wrote of. I think there are more. Read those. I like short stories. They had action, and description of the world. LeGuin didn't really describe the world much in the 4 previous books.
5. The Other Wind: I've read it once, maybe a year or so ago. I remember I enjoyed it, but unlike the others, it did not give me a lasting image of itself. It did have a nice change of themes from te 4th one and start up on dragons and magic again. Maybe I have to read it again.
Anyway, as you see, I don't have a very good vocabulary to describe her works with, but by all means these are among my favorite books/series.
And I've yet to read the Dispossessed.
"I think I just had an evilgasm." -- Lord Xykon, The Order of the Stick #197