Congress returns with hefty to-do list

They've been away from Washington for more than two weeks, but Congress is finally back on the job.

Both chambers of Congress are back in earnest this week to begin the second year of a session noteworthy for its rancor and sluggish productivity.

(Read more: Congress lets 55 tax breaks expire at year-end)

Here's what's on the to-do list for lawmakers as they return to Capitol Hill.

Paul J. Richards | AFP | Getty Images

1. Unemployment insurance: Senate Majority Leader Harry Reid says the chamber will hold a procedural vote Monday on a bipartisan proposal to extend long-term unemployment benefits to 1.3 million jobless Americans whose aid expired at the end of 2013. The plan put forward by Sens. Dean Heller, R-Nev., and Jack Reed, D-R.I., would offer a temporary extension of the federal benefits that kick in when state jobless aid runs out. It's not clear whether that proposal , which is backed by the White House, has enough support to pass the Senate, and it faces stiff opposition from House GOP leaders.

2. Obamacare: The dawning of a new year hasn't changed the Republican appetite for legislation to modify the Affordable Care Act. House leaders have said they'll schedule a vote on legislation to require possible cybersecurity breaches involving the HealthCare.gov website to be disclosed to the public. The Center for Medicare and Medicaid Services, which is responsible for the website, says users' privacy is already "a top priority."

3. Immigration: After the Senate passed a comprehensive immigration bill last summer, the effort fizzled when House Speaker John Boehner flatly refused to bring the sweeping proposal up for a vote in the House. But Boehner and other House leaders, eying the changing demographics of the American electorate, have signaled that they want to get some kind of immigration legislation passed this year through a "step-by-step" process, and pro-reform activists were heartened when Boehner brought a longtime immigration legislation expert on as a staffer last December. But any House-passed legislation may not be enough to meet Democrats' demands for a path to citizenship or legalization for most undocumented immigrants.

(Read more: Lew warns Congress of February debt ceiling deadline)

4. Debt ceiling: A budget agreement passed last month by Congress might have settled the question of government funding through much of 2015, but lawmakers must still wrestle with how to authorize increased borrowing to meet the government's existing obligations. Raising the debt limit is likely the more vexing question, though. "We don't want nothing out of this debt limit," Wisconsin Rep. Paul Ryan said last month in anticipation of the mid-February deadline by which Congress must approve new borrowing. "We're going to decide what it is we can accomplish out of this debt-limit fight." Obama, however, remains steadfastly opposed to negotiating over the debt limit, setting up a frenetic few weeks of posturing and negotiations on the issue.

5. Farm bill: House and Senate negotiators have been working since October to hammer out their differences on a farm bill, a massive piece of legislation affecting food and agriculture policy. Spending levels remain the largest holdup between the Republican House and the Democratic Senate, including some $20 billion in cuts to food stamp programs favored by the GOP and decried by Democrats. Negotiators in a formal "conference" committee to produce a final compromise bill say they're nearing an agreement, but the longer they wait, the larger the consequences—like a projected spike in milk prices—for farmers and consumers alike.

6. The next Fed chair: Before departing for the holidays in December, the Senate scheduled this week's final confirmation vote for Janet Yellen to become the next chair of the Federal Reserve Board. Though some conservative detractors of the Fed and its efforts to prop up the economy, last month's vote to end debate on her nomination all but ensures Yellen will win the majority needed to ensure confirmation.

(Read more: Fed's Plosser at odds with Yellen's policy approach)

—By Carrie Dann and Michael O'Brien of NBC News