Two major updates centered around providing better security for Twitter users. Hurrah!
Update #1: OAuth Requirement
OAuth, short for Open Authorization, is a protocol that enables users to grant access to their accounts, without giving their usernames and passwords. It can also be used to grant limited access only.
All third-party apps are now required to use OAuth, rather than asking for a username and password.
A list of the apps that have access to your account can be found at http://twitter.com/settings/connections. From here you can also revoke access to your account.
What this means:
By requiring OAuth, your password will not be given to, or be stored by these applications.
Update #2: Standardized URL Shortening
Twitter's link wrapping / URL shortening service t.co will be in full effect for all links found in tweets by the end of the year. You may begin to see them already for a select number of accounts.
Twitter Help Center:
A link converted by Twitter's link service [t.co] is checked against a list of potentially dangerous sites. When there's a match, users can be warned before they continue.
What this means:
By wrapping all links via t.co, the chances of clicking through to a malicious website is reduced.
Both of these new features will benefit the Twitter community in terms of security. This is a welcomed update given the number of new users joining Twitter every day.