I'm glad to blog (and "reshare) that Sage 5.4 is available now.
Some random picks from the release notes:
- notebook internationalization
- 4ti2 interface
- MathJax instead of jsMath
- Bijection between Rigged Configurations and Crystal Paths
- new features in group algebra category
- non commutative symmetric functions
- Update Cremona's table of elliptic curves to 270000
- Plancherel measure of an individual partition
... and much more besides even more bugfixes :-)
And I suggest you to follow Sage at Google+ to stay in the loop.