Daily Kos contributor DemFromCT provides an overview of initial polling after President Obama's health care speech last night (note that Daily Kos is a left-leaning website).
Rasmussen, whose polls I've suggested lean right, reports 44% support for the Obama/Democratic reform plan from a poll in which "the overwhelmingly majority of interviews... were conducted before the president’s speech to Congress Wednesday night." Rasmussen adds that it "will be tracking support for the proposals on a daily basis over the next several days to measure what impact the speech has on public opinion."
Gallup's daily poll has Obama's overall job-approval rating at 51%. Given the salience of health care reform at the moment, one might infer that any upcoming changes in his job-approval numbers could be attributed to the speech.