The Royal Institute, your friendly neighborhood language regulating organization, is all about the dissemination of knowledge. Their website is, frankly, not very good (too much style over functionality--their fancy menus don't display correctly in any browser but IE, blech), but I'll be darned if it isn't packed with goodies. Difficult to access, often half-baked goodies, but goodies nonetheless.
Case in point: classifiers. In Thai we know them as ลักษณนาม [ลัก-ษะ-ณะ-นาม, in case the four consonants in a row was throwing you]. As the Thai word indicates, they are a type of นาม (noun, though this word also means name), which tells you a characteristic (ลักษณะ). So, ลักษณะ + นาม (the vowel disappears because of สมาส combining rules).
Now, classifiers can be quite a chore to remember. I mean, how often do you use กระบอก, the classifier for gun? Or remember that a pair of pants is only a ตัว, but a pair of socks is a คู่? And many a learner forgets, in the heat of the conversation, that a pencil is a แท่ง but a pen is a ด้าม.
There is some research that suggests that native speakers don't employ nearly so complex a set of classifiers as the textbooks would lead you to believe, and use a lot of generic and repeater classifiers (nouns which can be used as their own classifiers, like ร้านร้านหนึ่ง "a store"). Interestingly, it also shows that younger speakers are better at using the Royal Institute's prescribed classifiers (presumably because, statistically, younger Thais are more well-educated than their elders). In my uninformed opinion, I find it's a matter of situation. In a more formal situation, or especially in writing, it's more important to know the standard. In informal conversation, it's easy to get by using a lot of อัน and ตัว.
Which all brings me to this link. It is the full text of the Royal Institute's useful (if unimaginatively titled) booklet, ลักษณนาม ฉบับราชบัณฑิตยสถาน (roughly, The Royal Institute Book of Classifiers). It's the text of the sixth printing, to be precise. Kudos to them for putting it online. It is organized alphabetically by the word you want the classifier of. In other words, look for นาฬิกา to find เรือน. The most glaring error is the lack of searchability, followed closely by the decision to arbitrarily number the 22 pages of text, sometimes with multiple consonants-worth of classifiers on one numbered page. Even when you know the letter of the alphabet, you still have to hunt around to find exactly which page it's on. The next obvious shortcoming is the inability to see what words share a certain classifier. For example, to be able to look up in one shot all the words the Royal Institute says it's okay to use ตัว as a classifier for.
In an effort to remedy this, and completely without the Royal Institute's knowledge or permission, I've taken their text and put it in a Google Spreadsheet, viewable here. I've divided it up into different "sheets" by letter. This doesn't solve all of the problems, but it's a start. This should serve to make the Royal Institute's date more valuable to language learners like you and me. (Feel free to contact me for the XLS or DOC or TXT files I made from the RI data.)
And let me know in the comments if you find a particularly interesting classifier you didn't know existed before.