Someone had mentioned a 30-year forgiveness period for Income-Based Repayment (IBR); it's actually 25 years' worth of on-time payments. Not a huge difference, but a difference nonetheless. However, a key point is that the discharged loan amount(s), to the best of my knowledge, are then taxed as income. Thus, if you've been making IBR payments that haven't even covered accrued interest and end up having something like $200k discharged, it's going to be a very rough tax year for you if you haven't been saving up in anticipation of that.
Public Sector Loan Forgiveness, as mentioned, discharges the remaining debt after 10 years and the discharged amount isn't taxed. No one's actually made it to the 10-year point yet, but the first crop of folks should be getting there within the next couple years. I imagine a pretty large clusterf*ck when that happens. The biggest issue will be all the changeovers that occurred when loans went from federal to private managers, and relatedly the inconsistent documentation criteria by various loan managers. I foresee a whole bunch of folks who're thinking they've hit the 10-year mark being told that they don't qualify for X or Y reason, and that they still need to make Z number of payments (or that they were never actually enrolled in the program in the first place).
There are various other loan repayment assistance programs as well. The VA offers loan repayment as an incentive for certain new hires (i.e., they basically give you a set amount of "extra" money per year, in addition to your salary, that goes straight to loan repayment; I think usually around $10-20k). Similarly, the National Health Service Corp offers $30-50k in repayment funds for each 2-year block of full-time service in approved underserved areas. I don't know if you can work for more than 2 years, though. Also, NIH offers loan repayments of up to $35k/year for MD and/or PhD researchers working in approved topic areas (e.g., clinical, health disparities, pediatric). And then there's always military service.