Marking my place too; though my DS will be a bit older at 2.10 years when DC2 arrives.
My ideas so far are:
Reading
Duplo
Toy vehicles
Train set
Sensory play eg playing with rice, lentils, pom poms, pebbles, shells, lolly sticks, straws, ribbons, pine cones etc. Hiding objects in sand / boxes of rice can be fun. Chucking straws about is fun & easy. Putting items into jars / cups / bowls / egg boxes / ice cube trays can be fun for younger toddlers. There are loads of ideas for 'invitations to play' on The Imagination Tree (and more in-depth ones on her blog)
Water play - DS used to spend ages stood on the toilet lid playing at the sink while I was in the bath (a good place to feed baby!)
Jigsaws
Playdough
Magnets (shapes, letters, numbers, magnetic pom poms or lolly sticks)
Throwing soft balls into a corner of the sofa (ball pool balls are great for this), or collecting / emptying into a large box
Drawing / colouring
Saucepans / toy kitchen
Roll of sellotape and a few kitchen roll tubes / egg boxes
Wooden building bricks - good for knocking down
A long tube and some vehicles can be fab - we've had poster tubes, curtain rail packaging and even wrapping paper tubes if your cars are small - just tip up at one end and you have a great ramp. Works with balls as well.
Divide normal toys into 3 or 4 groups, put all but one group away and circulate once a week (or whenever they seem to be losing interest in the current ones). It works a treat, and they play with them for much longer at a time. I do this with books as well."
The treasure box can contain anything which they might enjoy - just having something saved specially for feeding time can be enough to keep their interest.
I have a sling too, so hopefully I should be able to get reasonably involved in DS's play, and get out of the house.