An article giving examples and explaining the usage of stance markers and adverbials.
If in doubt about how to classify a word, it’s probably an adverb. Likewise, if a sentence element is elusive, it’s probably an adverbial. Robert correctly classifies phrases like as it were, so to speak, and if you will, as adverbials, but they are only one sub-set of what is itself a sub-set of the huge set of all adverbials. Biber, et al., in the hefty Longman Grammar of Spoken and Written English, have a whole chapter on what they call stance markers, that is, ways that speakers or writers express their attitude to, or evaluation of, or commitment to, what it is that they are saying (or writing) and I think this is the best way of classifying these handy little expressions.
Stance markers include stance adverbials, which in turn comprise single adverbs, as in Thankfully, it stopped raining or I’ve seen it before, actually; finite clauses, as in It was very tasty, I must say, and Joe has been sacked, it seems; non-finite clauses, such as to put it bluntly, so to speak; and prepositional phrases, such as as a matter of fact, and for all I know. Notice that these expressions all take the form of fixed, or semi-fixed, phrases – the famous lexical chunks. For example, so to speak is a fixed phrase, in that you can’t substitute tell or talk for speak without it losing its idiomaticity. Likewise: to put it bluntly, and Robert’s two other examples: as it were and if you will. For all I know, on the other hand, allows slight variation in the verb slot: for all I care.
Another characteristic of the examples Robert cites is that they all function as tags. That is, they are added as a kind of afterthought or qualifier to the substance of an utterance, filling the optional 'tail' slot that exists in spoken – but not written – language. Question tags are just one kind of structure that fills this slot; stance markers are another.
As for a list of 'these things', I can only offer a few of the more common ones, and/or the ones that are part of my own 'idiolect':
I dare say
by and large
I'll be bound