HI K.,
One thing that I have loved, is our neighborhood does a play group once a week. We do ours on Mondays at 10am and most of the activities are really simple such as going to the park, riding bikes at someone's house, planting seeds in a cup of dirt, doing a craft project. There are 6-8 mom's who get together with their kids--all ages, but mostly under 8 years old--the mom's trade "hosting" and one of the mom's makes a monthly calendar. The calendar let's us know 4 weeks out what we are doing and there are some fun "theme" parties for Halloween or for the 4th of July. It's cheep and fun and my kids get to interact with others and so do I.
Another thought is to check out activities such as gymnastics, in-door soccer, basketball, swimming and such at a community rec. center. For fairly inexpensive you get a month's worth of activity on another day of the week.
With these 2 days of activities and Pre-school, we keep busy and my kids have something fun to look forward to. Good luck!
:) M.