I know some of these were already mentioned, but these are 3 organizations that I have dealt with, so I know they are amazing: Tomche Shabbos {http://tomcheshabbos.org}, Chai Lifeline {http://chailifeline.org/}, and Partners In Torah {https://www.partnersintorah.org/}.
In Tomche, you can volunteer in the warehouse packaging or they also have drivers that do the runs Thurs nite to the homes, or even just collecting for them.. I know that with the economy, they are struggling to continue providing as much as they do.
In Chai Lifeline there is also a variety of things you can do; they have big sibling-little sibling programs; they have respite -where you volunteer in hospitals overnight/during the day/for shabbos- to stay with a child.. there are many different programs.
In Partners in Torah, they pair you up with someone of similar educational background/job type etc.. and you learn with them once a week.
Of course, all this depends what type of thing you are interested in volunteering in.