Is there any web site or other resource that would allow me to find the
least expensive air travel in the US regardless of date? IOW, I'm
completely flexible as to dates and I'd like to find the least expensive
fares to a destination. All of the major sites that I use ask for a date
(or at least a narrow range of dates before they search fares! I'm a
retired "senior citizen" (translate that to "dirty old man" if you want)
who has a lot of free time but not a whole lot of money who likes to travel.

TIA!