I don't know any major Eastern European medieval kingdoms, so some of those examples might be cool.

In the Kingdom of Hungary the general lack of a baronage at least after Caroberto defeated the oligarchs. Also the lack of titles and complicated hierarchies. Later on German titles were adopted (Graf to gróf etc. basically the Habsburgs introduced these after the Middle Ages) but I am mostly talking about the era of Ludovicus Magnus or Sigismund. There weren't really titles like Duke or Count. Noble families were generally in direct dependency from the King. Titles were administrative titles, that of a job, not that of an aristocracy. E.g. the nádorispán, usually translated as a comes palatinus so technically a Count but actually it was a temporary administrative position. Another position, roughly translatable as governor, was the Bán, e.g. that of Croatia. There were big families with lots of lands and a certain sense of distinction between upper and lower nobility, and of course it was the big families who usually got these positions - except when sometimes a low-ranking but bright Italian guy did it - http://en.wikipedia.org/wiki/Pipo_of_Ozora . Anyway it did not ossify into ranks of aristocracy or chains of feudal fealty. Most strategic castles were owned by the King. You could say that it was a bit like later Absolutism, the King's rule not much disputed and barons did not have a lot of power. Of course there was the Golden Bull http://en.wikipedia.org/wiki/Golden_Bull_of_1222 but nevertheless after Caroberto power centers independent from the king did not develop.

Only the king was allowed to donate land. So service to noble lords was paid by money, weapons, clothes etc. not land. These fighting servants, knights were called familiars. Familiars were still under royal jurisdiction and their relationship with their lord did not absolve them from loyalty to the king. Very rarely, familiars were granted land in a feudal way by lords, but a royal approval was a must.

Important: firstborn sons did not inherit everything, rather brothers owned the lands in common, or divided it up. This is funny, because Tocqueville said such a system would create a democracy in a few generations. It didn't.

It will be difficult to source it as 99% of the sources are in Hungarian such as Fügedi Erik's Ispánok, Bárók, Kiskirályok (Magvető, 1986) or Passuth's Tört Királytükör (1974), but if you want English you can try using the sources listed under the following articles:

http://en.wikipedia.org/wiki/Nobility_in_the_Kingdom_of_Hungary

http://en.wikipedia.org/wiki/Upper_nobility_%28Kingdom_of_Hungary%29

http://en.wikipedia.org/wiki/Nobility_and_royalty_of_the_Kingdom_of_Hungary

It's an unfortunate thing. Very few stuff is translated. Half of what I wrote was actually in my high school textbooks, nobody translates those.

To summarise the other (feudalism) thread: is not that the word itself is useless, but that the technical legitimacy of the term has become so in medieval historiography. The term purported to represent a contemporary phenomena when in fact it didn't exist for large portions of the medieval period and, when it did, was only an unrepresentative slice of the whole. As the focus on fiefs (the essential element of feudalism) developed over centuries of study the term took on so many conflicting definitions as to become meaningless. Each reader and historian comes to the term loaded with misconceptions that corrupt and obfuscate their understanding of medieval Western European society. As /u/AlanWithTea points out in the other thread. If historian have to describe the mechanism a structures, with examples, of their definition of 'feudalism' every time then why bother with the term at all?

There were superiors and inferiors in medieval societies, no one is disputing that (I hope), but just because there are superiors and inferiors this does not preclude elements of equality. Feudal hierarchy does not tend to allow for such elements of equality. Community and consent were much more important than merely having a higher rank than your vassal. There would be aspects were you shared elements of equality (kinship, martial honour, social or cultural traits, legal rights, spirituality, etc.).

Here is a post where a user set out a mid twentieth-century historiographical position on feudalism and I attempted to demonstrate exactly how and why feudalism was misrepresentative.

You know what the real problem is? It's that almost no one, that user above was an exception rather than the rule, who asks these questions has any idea what they think feudalism is.

for some people, king+knights=feudalism

Do they? What does that mean? I don't want to push my preconceived notion of what the public thinks feudalism was, any more than I would onto a historian.

Then tell [us] how major medieval kingdoms differed from this popular conception

How can we. I don't know what the popular conception is, likely for the reason cited above.

Tell me how England differs from feudalism, and France, and the Holy Roman Empire (and maybe even the individual states), and Spain.

The work has been done already (if you swap Italy for Spain). I have no desire to re-type a book out:

Susan Reynolds, Fiefs & Vassals: The Medieval Evidence Reinterpreted, Oxford, 1994.

It's like feudalism is a strawman built up a long time ago and everyone's saying, "That's not a real person," but they aren't saying how it's not a real person (no skin no bones no mind no organs etc.).

I'm not sure how you're misunderstanding that what we mean when we say IT IS NOT IN THE SOURCES is saying that there is no body!

From another comment:

Feudalism was 'created' by sixteenth-century lawyers trained in Italy studying from the Libri Feudorum ('the Book of Fiefs). The lawyers and antiquarians of the sixteenth- through eighteenth-centuries envisaged medieval landholding as centred on the fief. This was concept was soaked up by nineteenth-century historians and, in the twentieth-century, this exploded into a holistic analytical model which drew on northern French society and culture to create an 'ideal type' which could then not only be compared to other contemporary societies but to periods and places where fiefs and vassals had never existed as terms. This is a somewhat barebones sketch but I'm rather tired about discussing the subject. Essentially you're right, no king did say those types of statements. It was the development of a more professionalised legal class in the twelfth- and thirteenth-centuries which began the process of codifying the tenurial patterns and superior/inferior relations which would lead their sixteenth-century descendants to begin conceiving of fiefs, and later for historians to conceive of feudalism.