Getting There & Away
Sterna Bus 12/12a between Reykjavík and Jökulsárlón runs daily in July and August. You can take it one way (from Reykjavík, 8¾ hours, 12,000kr) or pick it up at various towns along the south coast. It returns to Vík after two hours at the lagoon; you can stay overnight there and return to Reykjavík the following day (return from Reykjavík 24,000kr).
Strætó Bus 51 between Reykjavík and Höfn runs twice daily and stops here. It simply drops off or picks up passengers, it doesn't linger. One way 11,500kr, six hours.
Reykjavík Excursions Bus 15 runs twice daily between the visitor centre at Skaftafell and Jökulsárlón (2800kr, 45 minutes) in July and August only.