Twitter is back but you should configure your Twitter with Hootsuite and Seesmic in case if twitter is banned again.
Following are the ways you can still use Twitter or access/unblock other blocked/banned sites.
Use SpotFlux. Download it and get all sites unblocked very easily. Using spotflux software is the easiest method to unblock sites in any country, even YouTube.
or use following proxy sites to open blocked sites in any country:
(Not all sites will be working with twitter as some block Twitter’s site scripts etc)