Assisting the community organisations who provide the most help for those in need and pass on funds to worthy causes ie: shelters/refuges, hospital fundraising groups, op shops/thrift stores, volunteer groups, disability services, churches, local charities, etc.
Visiting those who are lonely, disabled or isolated or setting up groups or activities for them is very beneficial and something to think about getting involved in.
Everyone can make time to help in some way or another... no matter how busy they are. Holding fundraising activities is an excellent place to start. It's easy to set up if you have the numbers to pitch in. Also, as you mentioned, clean-ups are a great way to put time and human effort to good use. Many hands make light work, as they say!
Just in general though, the little things people can do personally can make a big difference including smiling and politeness to as many people as you can each day, random acts of kindness (Google it for ideas!), helping friends or strangers out when you witness that they are struggling (without being asked or prompted!), giving compliments, doing something thoughtful for your family members or helping out that little bit extra without anyone telling you to, simply asking people how they are (and really caring about the answer!)... and just generally making time to CARE - in as many simple ways as possible. You can start small.