Those are probably the most obvious ligatures English has, but they aren't the only ones that are disappearing. The ligatures ﬂ, ﬀ, ﬃ, and ﬄ are being replaced by individual letters (and, as anyone who's tried to turn a pdf of a printed novel into an ebook will agree, this is in some ways a very good thing).
But at least the ampersand & is still to be seen from time to time. & is basically a joining of the letters e and t, which together make the Latin word for and.
Of course there's one ligature that's still used in just about every page of English that's written. In fact I've used it several times in this one.
It's the u-u ligature. Nowadays it usually looks more like a double v.
But we still call it, yes, double-u.
Thing to use today: a ligature. Yes, this is dead easy, isn't it? The word ligature comes from the Latin word ligāre, which means to bind.