While the USPTO marches to find consistency on patentable subject matter, I found this practice notice from the UK IPO dated December 8, 2008, dealing with computer programs in light of the recent Symbian decision (link). At first glance, this appears to be a more rational test than the "tied to a particular machine" analysis used at the BPAI under the post-Bilski era:
4. The Symbian judgment (especially paragraphs 54-56) provides an insight into what constitutes a technical contribution; in other words, a contribution that is more than solely a computer program. An important factor is what the program does as a matter of practical reality.
5. The Intellectual Property Office has previously recognised that an invention which either solves a technical problem external to the computer or solves "a technical problem within the computer" is not excluded. What Symbian has now shown is that improving the operation of a computer by solving a problem arising from the way the computer was programmed - for example, a tendency to crash due to conflicting library program calls - can also be regarded as solving "a technical problem within the computer" if it leads to a more reliable computer. Thus, a program that results in a computer running faster or more reliably may be considered to provide a technical contribution even if the invention solely addresses a problem in the programming.
6. It remains the case that whilst an invention involving a computer is undoubtedly "technical", in law the mere presence of conventional computing hardware does not of itself mean an invention makes a technical contribution and so avoids the computer program exclusion. This is in contrast to the practice of the European Patent Office, which the Court of Appeal rejected in Symbian.
Read the full notice here.