.: dimensional analysis tool
I wrote a programme that computes the dimensions (M, L, T, t) for an equation. I found this programme extremely useful when doing derivations of formulae, since keeping the dimensions of the LHS and the RHS in synchronization is essential. You can check the dimensions of any expression by dragging and dropping units onto the work area. You can also check the dimensions of just the numerator or just the denominator. If you have read and agree to the terms and conditions, click here [1.2 MB] to download the programme and here for a screenshot. If you prefer a portable version (one that does not need to be installed), please click here [1.014 MB] for the zip file.
.: on-screen ruler
I programmed a semi-transparent, on-screen ruler that I have found useful for web-page editing and building GUIs. The ruler can be resized using the mouse and is highly configurable. Right-click on the ruler to learn about options you can configure. I also provided several keyboard shortcuts that can improve your control over the programme. You can change units using a mouse wheel instead of the menu. The last settings you used are saved in the same directory as the executable. If you have read and agree to the terms and conditions, click here [544 KB] to download the programme from download.com or, if you don't like installers, get the portable version here [366 KB] and unzip the files into a folder of your choice.
.: gaussian curve fit
Here is an article on performing regression on non-linear data. Several readers asked for a spreadsheet that showed how to implement the calculations in Excel. Click here to download an excel spreadsheet or here to download an OpenOffice spreadsheet containing a worked example (use at your own risk). I created a column of data that had an approximately normal distribution with a mean of about 100. I created a histogram from the data, and computed a best-fit gaussian distribution for the histogram using the equations in the article.