I have a 16 week old baby girl. I noticed that if I just "check in" with her periodically while I'm doing housework, she's fine. She will play on her own anywhere from 30 - 45 minutes with the periodic check in to get a smile and a giggle. I also notice that some toys she will stay with longer than others. So, if I need to get something done I will give her those toys and then she won't see that toy again for awhile so it stays fun in her mind.
Sometimes transitioning from one spot to another is hard on her. In that case I let her "yell" at me about it for a bit and then after she's got that off her chest she will typically settle into the new surrounding. Only if she's tired or hungry will she continue to yell at me.
Some things she really likes to do: anything hanging over her head she loves, being on tummy for short period of time looking in mirror, being a "big girl" and sitting up to play (she is really starting to like this and will sometimes cry if I lay her back down!) If she gets fussy and I know she's not tired or hungry I will take her outside to watch the trees and grass - she absolutely loves this! She will lay on a blanket and just stare at everything!
HTH!