I've been learning MS Excel and macro creation to analyze diesel emissions, so I have made spreadsheets that solve Kepler's equation, plot the discrete logistic, &c, as practice lessons. However, with the VBA macro language, serious scientific computing can be done and some people apparently are doing it. There already are a lot of functions in Excel that overlap NR and more are available as an "add-on" But there might be a market for NR functions and macros that could enable Excel to compete with packages such as MatLab, Mathematica, &c. Excel provides fairly good graphics capability and supports 64-bit floating point. There is at least one academic offering a tutorial on doing scientific computing in Excel. There may be some concern about how long the VBA macro language will be supported, but MS has developed a similar Visual Basic.NET Office System Tools so that the jump should be no worse than that from Fortran 77 to 90 or C++. The name of the academic and other info may be gleaned from Bill Jelen's website (he wrote the book I bought, "VBA & Macro for MS Excel", Que, 2004): http://www.mrexcel.com/index.html
The zipped discrete logistic Excel file is attached.

There is another resource that is very good. It is entitled "Advanced Excel for Scientific Data Analysis" by Robert de Levie.
I write in VBA about 30-40 hours a week and I am very confident with Excel and when one of my macros throws an error, to me, I just fix it. The most common error you can encounter is a type-mismatch. (This can occur by simple clicking on the cancel button on an input box.) However, my fellow office workers (engineers, chemical and mechanical) do not posses this ability, because of this I switched to using Access and spend much more time error trapping my forms and code in order to have as flawless a program as possible. I have encountered more people who "think" they can use Excel than I have "real" users. For instance, my boss knows how to force convergence by changing the settings in the tools options box but he can't create a simple graph. The other problem occurs when one tries to copy the entire spreadsheet and paste it into another sheet in the same workbook without realizing that all of the references in the recorded/written macro code is reference the original sheet. Lastly, the most dangerous part of a spreadsheet is the fact the multiple copies are required per user and I don't need to explain what this can cause. LOL
Anyways, I enjoy both Excel and Access and I have a love for C++ so if you ever need advice or simply someone to bounce an idea off of let me know.