As Cannonade wrote, a label might be what you want. But since you explicitly mentioned branching in your question, you should be aware of the differences between a label and a branch:
With a label, you simply mark the current state of all files in your source safe database (the repository). If you created a label "V1.0", you can now at any time easily retrieve exactly that state and rebuild the V1.0 release for example.
With a branch, you create a copy of the current state of your repository. E.g. if you create a copy named "1.0", you can then continue with the development e.g. towards V2.0. Should you ever need to fix a bug for V1.0, then you can do this on the "1.0" branch.
So branches should be used to work on different versions of your projects in parallel. Labels should then be used to mark special versions on your branches (e.g. the ones used to create a release).
One last note: SourceSafe does not have a specific "branch" command. Instead you "Share" your solution and select the option "Branch after share". You can find more information about it in MSDN.
And a very last note: We stopped using SourceSafe about 1.5 years ago and switched to subversion (which is opensource and free). Have a look at subversion or other solutions. I can not imagine ever going back to SourceSafe.