I don't like to get new equipment if I have old equipment that still works fine. My Asus A2500S laptop is now more than 10 years old, and although it has received a few small repairs and a memory upgrade over the years, it still works fine. Its Pentium 4 Mobile processor may be a power hog, but it's not slow. Its main bottleneck is memory. The full Ubuntu is getting a bit too heavy for the old guy, but Xubuntu still runs like a charm. On the other hand, at over 5 kg (including power-supply) the thing is HEAVY.
One of the drawbacks of a monolithic kernel is that you're often stuck with outdated drivers that don't work for your hardware. Even if a fix is available upstream, there's no easy way to update just a single driver. Luckily, LinuxTV now at least offers a script to automatically recompile the entire Video4Linux subsystem against your current kernel version, and replace the default modules with the latest versions: http://git.linuxtv.org/media_build.git
Shapefiles are a format developed by ESRI (the makers of ArcGIS) to store and share geospatial data. Many interesting datasets are freely available in shapefile format. Shapefiles can be viewed with a number of freely available applications, such as ArcGIS Explorer (which requires the .NET framework or Silverlight) or ArcReader (which is multi-platform but closed-source).
It seems hard to believe, but fax-machines have been around for over a century, and the current digital fax technology stems from the 1980s. Back in the days, for most people faxing a document was the only fast alternative to sending it by normal (as in non-electronic) mail. These days, as multi-function printers and copiers with scanning-capability are becoming more widespread, fax-machines are slowly obsoleted by the ability to easily scan documents as PDF and send them over e-mail. Nonetheless, every now and then someone asks me if I can send or receive something by fax.
PDL is an extension of Perl for numeric/scientific data processing. It was originally developed by astrophysicists as a free alternative to packages like IDL and Matlab. It's quite fast and memory-efficient, and very powerful. I've found it to be most useful in cases where you have to mix data-processing with the strengths of Perl (anything involving list & hash-operations, regular expressions and/or text-parsing or output). Its main drawback however is that it has a rather steep learning-curve, because the documentation is quite fragmented and not always clear.
I've written a fast perl/PDL implementation of UPGMA data clustering for very large datasets. The problem is that existing clustering packages have difficulty handling datasets with more than a few thousand data points. Especially the distance matrices tend to become a problem. For example, clustering the outcome of a 300x300 grid-based simulation (90,000 data points) would require a (non-sparse) distance matrix of 8.1 billion entries. This would use over 30 Gb of memory when stored as 4-byte floating point values.