Im a SAHM to a 20mo son and 6week old daughter. Two doesn't fix the boredom or sense of isolation. The isolation can feel a little worse though because it's so much harder to get out of the house with a second baby. The monotony of feedings, diaper changings, and house cleaning etc can become so automatic that you don't notice it anymore. I was talking to a girlfriend (no kids) on IM the other day and she asked what I was doing, and once I wrote it out, I got tired just looking at it, and my son was napping even. I didn't realize or even notice just how much I can accomplish in two hours. I also try to get out of the house every day, though with the new baby it's harder, we at least walk to the park every nice day. I try to get in playdates with friends who also have kids. One of my girlfriends and I meet with the kids once every other week for a "Coffee date" and let the kids entertain eachother so that we can at least have some adult conversation. Were talking about starting a M. and tots book club for extra stimulation. Like a previous poster its hard to be excited about a puzzle you've put together 100 times. So no you're not alone in this feeling.
Other activities....
*Make playdough,
*sidewalk chalk (it's getting nice so it can be fun),
*Nature walks-collecting leaves, sticks and rocks and using them in an art project at home - We have buckets in the garage where my son keeps his collections from our walks, and when it's rainy we take the buckets and sort them out and use the contents to make things.
*Building forts is always fun.
*Story time at library's and Barnes and Noble.
*gardening - my son loves to dig in my garden so I bought him his own shovel and gloves
These are a few things we do to break up the week. Hope it helps.