I've asked the same question before.
However, I'm not really sure if I'm correct about the usage of these two words. Please help me.
a. I know some good pubs around here.
indicates the speaker doesn't have any specific pubs in mind.
He might or might not know where the pub is, but he knows there are some.
The speaker seems kind of ambiguous.
b. I know several good pubs around here.
shows the speaker has some specific pubs in mind, and he/she can
name the pubs, from which the listener can choose.
The person in a) knows the pubs so they are specific, but the number isn't; it could be 3, say. 'Several' implies a decent number; somewhere around half a dozen or more. B) sounds like the more serious and dedicated drinker; if the first few are full, a) may run out of ideas, but b) will still know of more places to try.