There is great info on the wikipedia page on lactose intolerance
en.wikipedia.org/wiki/Lactose_intolerance. Looks like I had the wrong understanding of why yogurt is alright - according to this, the yogurt culture contains lactase! Also, Greek yogurt is strained, so most of the remaining lactose is taken away with the discarded liquids. I've been lactose intolerant for many years, and I know pretty much right away when I've eaten too much lactose. For me, it's a matter of upper GI gas and some nausea, and it passes within 30 minutes or so. Others get diarrhea, which is clearly more of an issue than what I experience.
Dairy productsLactose is a water-soluble substance. Fat content and the curdling process affect tolerance of foods. After the curdling process, lactose is found in the water-based portion (along with whey and casein), but not in the fat-based portion. Dairy products that are "reduced-fat" or "fat-free" generally have slightly higher lactose content. Low-fat dairy foods also often have various dairy derivatives added, such as milk solids, increasing the lactose content.
ButterThe butter-making process separates the majority of milk's water components from the fat components. Lactose, being a water-soluble molecule, will largely be removed, but will still be present in small quantities in the butter unless it is also fermented to produce cultured butter. Clarified butter, however, contains very little lactose and is safe for most lactose-intolerant people.
Yogurt, frozen yogurt and kefirPeople can be more tolerant of traditionally made yogurt than milk, because it contains lactase produced by the bacterial cultures used to make the yogurt. Frozen yogurt will contain similarly reduced lactose levels.
CheesesTraditionally made hard cheeses, and soft-ripened cheeses may create less reaction than the equivalent amount of milk because of the processes involved. Fermentation and higher fat content contribute to lesser amounts of lactose. Traditionally made Emmental or Cheddar might contain 10% of the lactose found in whole milk. In addition, the ageing methods of traditional cheeses (sometimes over two years) reduce their lactose content to practically nothing. Commercial cheeses, however, are often manufactured by processes that do not have the same lactose-reducing properties. Ageing of some cheeses is governed by regulations; in other cases, no quantitative indication of degree of ageing and concomitant lactose reduction is given, and lactose content is not usually indicated on labels.
Sour creamIf made in the traditional way, this may be tolerable, but most modern brands add milk solids.