I don't know how current this information is, but according to the city website the South End CC has playgroup 2 mornings a week. Usually there's a nominal fee (like $1 or $2). You might want to call the contact person on the page to see if it's still running before trying it. We did playgroup tons when my older girls were very young.
http://brandon.ca/community-centres/south-end
It's too bad that some of the old playgroups have shut down, but at one point there was a playgroup every day Monday to Friday. It was wonderful. However, people move on and no one takes over the groups, so they go away. Playgroups used to also be held at St. Matthew's Cathedral and West End CC. If someone was interested in getting another one going, those might be good places to start when looking for space (nudge nudge, hint hint).
Also, Elspeth Reid has a playgroup on Friday mornings. It costs $2 if I remember correctly. You should call them to find out the details - it seems to be they ask that you only come every other week so that it's like 2 groups of people, to accommodate everyone. They also sometimes run programs that are of interest for the kids.
The library, while it's not "running around" often runs story time for kids as young as 0-18 months, and then 18-36 months, etc right up to school age. My kids always had a lot of fun, they read a story and then a related craft. I think they even got a themed snack. Check with children's services to see if any groups are running right now or when you can expect the next one to start. There is no fee.
And finally, like others have suggested, is just to go outside, even if it's just for 15 minutes. It helps break up the day. Also, try some physical indoor activities - Pinterest has tons of ideas for indoor games to get your kids moving and grooving. Our kids loved the mini indoor trampoline, they're cheap at Wal-Mart. Saves my couch too so they're not bouncing on it.
Have fun, and remember... spring is just around the corner!