My son was 21 months when my daughter was born.. he was still having 2 hour lunchtime naps when she arrived and, after the first few days of me thinking I should tidy the house etc when they were both asleep, I learnt to sleep whilst they both did and the house just looked a little bit of a mess for a while.
My son never really watched much tv until my daughter was born, but we soon learnt to love cbeebies - its educational don't you know?!! We sat and watched together for quiet time, or I read him books whilst DD slept (nice chilled activity that entertained him for hours). Also the cbeebies magazines (or peppa pig or anything like that) are great to keep toddlers occupied for a while - stories, colouring in, stickers etc.
We had (still have) a good network of friends who kept us entertained too, lots of afternoon's drinking tea with friends & their kids.
There is no denying that it is hard work at times, but totally worth it - my son & daughter now share a bedroom (ages 4 and 2) and absolutely ADORE each other, am convinced the small age gap has helped massively. Now expecting no.3, with a slightly larger gap (2.5years) between 2nd & 3rd. GOod luck, its a wonderful time that will zoom by, however tired you might feel at the time!