There has been some good posts recently on the web and HBL discussing what objectivists should do to help spread Objectivism. It goes without saying that donating to ARI and its Free Books for Teachers program would be an excellent place to start. Also, at the ARI site click on the 'Support ARI' tab then the 'contribute' tab for more ways to contribute or click on the 'campaigns' tab for things to support.
There are other activist efforts to support as well. There is FIRM (Freedom and Individual Rights in Medicine) and AFCM (Americans for Free Choice in Medicine) both of which could use help. The activities of these are sometimes updated at NoodleFood.
Writing to one's political representatives and LTEs to papers and mags helps as well. What with the Dems controlling Washington now I think it is vital that Objectivists concretize everything. If the powers that be utter a desired principle, then letter writers need to give concrete examples of what that principle will look like in the future. And if these same powers advocate a certain concrete activity, then writers need to identify the principle on which it is based, then concretize even more examples into the future. Projecting examples into the future is critical for I am convinced that anyone who can even partially think in principles will see events unfolding before them and be able to say something like "Hmm, they said it would look like this."
I know from experience that writing LTEs to papers shooting down what seems like an endless stream of awful ideas can get to be depressing. But to really feel good about oneself I recommend getting behind something good and giving a push. For example, put together $59 and give a gift subscription to the Objective Standard to your local public library or community college library. Or get behind some Objectivist newsletter like the Undercurrent and drop off some copies at your local college. Because education is so important, whenever Lisa VanDamme sends out her newsletter Pedagogically Correct, I post it in its entirety on my site and leave it there for a minimum of 24 hr. but usually 3 days. Know of an Objectivist radio show? Fire off an email to the Director of Programming at a talk radio station in your area extolling the virtues of that show and how it would be a great addition to your community's talk radio. Even when it comes to LTEs, sometimes, when I see a rational op-ed I'll send a short LTE to the effect "Kudos to professor Smith. His op-ed on inflation was spot on. We need more intellectuals like him." Giving the good a push re-charges one's batteries to keep on fighting the good fight.
I have been a little remiss on some of the suggestions above. So, I have decided that my 2009 New Year's Resolution will be to double my efforts at getting behind the good and giving a push.