Budget Spreadsheet (Excel) - monthly budgeting spreadsheet. We used this spreadsheet while we were paying off debt.
You Need a Budget - 34 day free trial. See my review for more details. We graduated to this after five years of using the spreadsheet and love it!
Every Dollar - Free version available, but if you want to connect your accounts and have support, there is a paid version as well.
Debt Snowball
Debt Reduction Calculator - I use this when I work with others. It has the flexibility to change the order of your debt snowball as desired.
What's the Cost - We used this website when we were paying off debt. I liked that you could login and save your snowball and edit it from month to month. It's an ancient site, but does the trick. I would have used the debt reduction calculator above if I would have known about it at the time.