1. Life of the mind. Taking a few minutes a day to work on a longhand story in my notebook while the small child is awake and running around. Listening to podcasts while I do more around the house can help keep me from feeling quite so locked-in, and doesn't scream "bad parent" like having the TV on. Likewise, reading. My ebook reader has been a lifesaver, though reading paper books would be hard. There are also a ton of free online classes that could be worked on while the baby's sleeping (note to self: http://cloudscudding.livejournal.com/
2. Contact with other adult, non-baby-centered humans. I have a couple of writing-related groups that meet once a month, and that helps a lot. Having friends over for dinner (if she or someone else in the household likes to cook) or going out for dinner (if they don't) can be managed with or without small children.
3. Getting out (with baby)! Taking a walk around the block, even. Once small child is walking, finding places that are good for baby-socialization: library storytimes (often with bonus playtime), awesome children's bookstores, coffee shops with popular play areas. Museums (also good for life of the mind).
4. Defending my time. When the kids are sleeping, that is my time for working on creative endeavors. It is not the time for doing household chores or prepping dinner or anything else, and if that means other things don't get done, that's just too bad. Related to that--
5. Rearranging my time. There is still time to do creative things, it just may not be in the same amounts or time slots as previously. This is the part where a supportive spouse can really make a difference, both by flipping any "I can't X" statement into "How can you X?" A spouse offering a consistent extra time slot that can be planned upon can help--every Saturday afternoon, say, or every Wednesday evening from 7 - 9 PM. And looking forward to that time can really help. This can be time at home to work, or time to go to a coffee shop alone, or whatever.
Most of this is stuff that only the SAHSpouse can choose to do, but basic spousal suggestions are: reinforce non-SAHM positive traits, schedule a regular time to take over childcare duties, divide household tasks explicitly to keep them from being automatically put on the SAHM plate, ask what needs to be done so the SAHM can do things she says she can't.