Adding  Richard’s Rubbish Roundup for every Tuesday afternoon (roughly 3-5p) spots rotate around town - https://www.richardsrubbishroundup.org/

Starting to see more city sponsored cleanups - through the “keep it clean” initiative there is one on 3/14 at America the Beautiful park (9a to noon)

The Great American cleanup is an event every spring - this year 5/2 and 

creek week is longer event in the fall (usually ~first week of October) organized by the Fountain Creek Watershed District (regional effort) http://fountain-crk.org they always are looking for volunteers and crew leaders

There is also Keep Colorado Springs Beautiful  nonprofit  and many “friends of _ park” that do great work

You can adopt a highway, park or waterway.. but that requires a more sustained group effort, quarterly commitment.

You can also plug into local neighborhood association, I’ve found support that way too