Ah, good thread. We've got two boys, 17 months and 5 months, and a lot of the things already mentioned on the thread are very familiar.
The nappy bin I'd wholeheartedly endorse (though ours is a different one, Angelcare, available through Argos and in supermarkets). Likewise, though we are not keen on dummies generally, at times for short periods they are invaluable. No 2 son is more of a dummy user than no 1 son ever was. We got a baby bath which has a shaped base to fit the baby which is much more convenient than a normal bath where you do have to hold baby in one hand. In our one the baby is supported by the bath itself.
I agree that vests are the clothes to buy, ones that fasten up the side are easier to work with than the more common ones that fasten at the crotch. If you are anything like us we were inundated with clothes (certainly for the first one, not so much the second) as gifts to the extent many were returned and swapped for bigger sizes as we had more than they could possibly wear before they outgrew them.
We borrowed baby monitors but have never used them. The house simply isn't big enough for us to actually need them. We did buy cot beds rather than cots but neither child is old enough for that to pay off yet. We also had a vibrating bouncy chair. No 1 son really liked it until he outgrew it. No 2 son hasn't been interested in it yet but then he is a more unsettled baby and doesn't like being left to sit in a chair by himself. We never had baby slings and used the cold water steriliser.