Unemployment — file this week, literally.
The clock
In most states your claim takes effect the Sunday of the week you actually file — not the week you lost your job. Some states will backdate for good cause, but the grounds are narrow and vary by state, so don't plan around it.
What waiting costs
Every week you wait can be a week of benefits you don't get back. File even if you have severance, and report any severance accurately when you file — let the state decide, don't rule yourself out.
Where to file
Start at the official finder: CareerOneStop Unemployment Benefits Finder — a U.S. Department of Labor (DOL) site.