Your question is ample to answer, and the fastest answer is: open your map, play with the star map to light the different stars according to some statistic and you find the "hot spot" you are more interested in.
Long answer: it really depends on the kind of hot spot you are looking for.
You want to find the largest amount of players congregate? That would be the aforementioned jita 4-4, the worst dump of EVE.

NEVER go there, esp at the weekend. It's the commercial center of EVE, but due to this it's lagged like hell, and I trained some levels in trade skills just so that I can do my business there without actually enter the system. Still, there is at least one commercial hub for each of the empires: oursulaert for gallente, amarr for amarr, rens for minmatar. There are others (stacmon, hek, agil come to my mind).
Then there are the mission hubs, i.e. where there are good mission agents. The most infamous/lagged is motsu in caldari space, but apart from that I am not into mission running so I don't know the others.
Then there are lowsec pvp hubs, and to find them I suggest you check the "ships destroyed in the last 24 hours" statistic. Currently THE action in lowsec is in tama, where FW battles are taking place and sometime some alliance drops capital fleets on top of militias. I WAS at the Massacre of Tama.
Given your past history, you might probably want to go stealing from miners in highsec, or go ninjalooting/salvaging in tama.
Then of course there is 0.0 but it's hard to find hubs there... Well, except when capital ships "congregate" to battle.
