The Fisher-Price Company has a pretty cool website that has loads of activities for those of us who work with very young children. This website allows you to choose your age group (1 month, 2 months, 6 months, etc) and then choose the domain you want to support (Cognitive, Social-Emotional, Physical). It then has tips and ideas for things you can do with your infant or toddler to support the different areas. There is also an area that describes what children this age should be able to do and what they might be able to do.
If you look through the “Cognitive” area, you will find lots of ideas about math to add to your repertoire.