Ok, so I can't find Harvard Taiwanese 101 (哈佛台語101) on books.com.tw (my preferred Taiwan based online vendor), but I have found it on
Sanmin.
(Honestly, it's not much of a loss not being able to find it much of anywhere. The book could have been much better with it's dealing of grammar.)
Also, here is a link to the other book I've recently bought from Taiwan:
Southern Hokkien: An Introduction by Fuehrer and Yang.
It's a good textbook, but it assumes some knowledge of some form of Chinese, and often does not give grammar explanations (well not explicitly aside from what is explained in the vocabularies to the lessons). But it does a great job at explaining vocabulary.
Unfortunately Spoken Language Services appears to be out of business now, but I would still highly recommend both
Spoken Amoy Hokkien and
Spoken Taiwanese both by Bodman, for those who can obtain these books. If you are to get only one text though, make it
Spoken Amoy Hokkien, as it has all of the grammar explanations and drills.
Spoken Taiwanese only has the main dialogue of the lessons rewritten into the dialect of Tainan; it does not contain any grammar or drills and is meant to be a supplement to
Spoken Amoy Hokkien. It is well worth a look at Amazon or eBay to see if you can get it for a reasonable price. These two texts focus exclusively on the spoken language, so only romanization is used through out. [We did talk about this book a bit upstream already, but no harm in adding this.]