Git

A distributed revision control and source code management system with an emphasis on speed.

Beginning Git

Try Git
Complete Git Branching interactive tutorial
Watch the Normal Workflow gitcast

You should be able to

Initialize a repository.
Clone a repository.
Ignore files.
Add a file to staging.
Unstage a file.
Check status.
View a diff.
Create a commit.
Push to origin.
Pull remote changes locally.
Resolve a conflict.
Create a branch.
Merge a branch into master.
Push to a remote branch.
Rebase origin/master into a branch.

Intermediate Git

Watch the Distributed Workflow gitcast
Read Chapter 3 of Pro Git
Read gitready articles that interest you

You should be able to

Add a remote.
Amend a commit.
Show a commit by SHA hash.
Stash changes.
Squash commits.
Create a tag.

Advanced Git

You should be able to

Cherry pick commits.
Reorder commits.
Keep either file in merge conflicts.
Restore lost commits.
Visualize commits differently using git log flags.
Visualize changes differently using git diff flags.

Ongoing Reference