Web tools I made that I think are actually useful

Every now and then I create a tool to solve some computer challenge I have. I like to create a web page interface so the tool can be accessed from anywhere or used by anyone who has the same need. Many of the tools I have on my web site are focused on geocaching puzzles or the annual Venona activities. Many of the tools are cipher or encryption based to help others test ideas in these Venona fun. Others are derived from those activities like the ciphermail program (I kept private for a year and a half) that I think are useful in some way.

A couple recent tools I think are actually useful.

• When gas prices were shooting through the roof, I created a Fuel Cost Comparison tool that allows you to compare the gas costs of two different cars. This is a simple formula and a simple tool. The value I believe it has is that is shows the significant value of going from a car that gets 19mpg to a car that gets 23mpg versus going from 23mpg to 27mpg or 27-35mpg (the fuel savings are much more significant in the lower range). At a friends request, I added the comparison between two cars that use different grades of gas at different prices. This showed him that it was cheaper to operate his lower mileage vehicle which used cheaper gas than his other car. This is a difference between saving gas or saving money. Sometimes you gotta make that choice.
• For fun, I wanted to make a Mortgage Payment calculator that shows the formula to calculate the payment as well as the formula used to calculate. Additionally, you can compare two interest rates to see, on one page, the difference. Now that it is done, I realize I need to add a second points value for the second interest rate.
• As noted above, I think the Cipher Mail is a cool tool. As I learned how to create and decode cipher text, I thought it would be fun to create a tool that can be used to create an encrypted email message that cannot be easily decoded. As with all ciphers, a pre-shared key between the sender and recipient must exist. Is this really useful? Probably not but the geek factor is pretty high!

So, what is on deck? I don't have a definitive list of useful tools. Here are some ideas.

• A simple interest version of the Mortgage Payment Calculator. Something someone who is buying a new car could use to get an idea what the payment would be based on multiple interest rates.
• Recipe multiplier. The basic idea is that you have a bunch of ingredients for a recipe and want to double or tipple or whatever. This tool would calculate the new quantities based on each ingredients measurement system.