The trick of going from upper intermediate to advanced and beyond is literacy (or complete immersion, literacy being a cheaper route). First recommendation is get a Nintendo DS with Kanji Sono MamaDe RakuBiki Jiten. That or a 600 dollar palm pilot with windows and download the kanji dictionary (or pay for it?) . This saves a ton of time looking up Kanji since you simply write it on the screen.
Second Rec.:
Kodansha's Talking about Japan 英語で話す「日本」Q & A
One side is Japanese, the opposite page is English translations. The cool thing about this book is it introduces a variety of subjects in short easy to digest articles. Perfect to get a solid foundation on each subject before venturing into deeper waters in my opinion.
Some subjects: Geography, Climate, Natural Disasters, History, National Anthem/Flag, Japanese Language, Emperor of Japan, Historical Periods past to present, Constitution, Governemnt, Economy Industry and Trade, Taxes, Police and Crime, Self Defense Force, Population and Families, Characteristics of the Japanese, Education, Japanese in the Workplace, Pensions, Health Care, Religions, Contemporary Culture, Traditional Culture, Clothing of Japanese, Culinary Life of Japanese, Housing in Japan, Holidays and Festivals, Marriage, Funerals, Leasure time and Recreation of the Japanese, Sports, and finally Daily Life.
As you can see just about anything covered in any classroom is included, at least at a basic level, within this book. Also as you make vocabulary lists from the articles you can check the book translation against your own translations. Personally I'd rather have this book under my belt with a small basic knowledge of everything rather than go into a class blind and get a super detailed article about some topic I've never even heard before.
Anyway, good luck and happy learning.
p.s. This is part of Kodansha's bilingual book series. They got like 20 different books, basic like this to super in depth, even ghost stories and old Japanese stories. Check em out.