That's a great suggestion! I'm not sure what exactly I think about it, but I'll just write some of my immediate thoughts:

1. It seems like both the cost and the benefits for one person are very low. Cost is likely less than $100 per year. It seems like the biggest VC projects have hundreds of thousands of volunteers, so one may contribute, say, about a thousandth of the effort. And then, it's not clear what the impact of the scientific project is.
2. Generally speaking, finding high-impact scientific projects is really hard. I would guess that most research being done is of very low impact.
3. It might be interesting to think of how the EA community might scale this up. Perhaps it would be great if we could rather cheaply get thousands of people to start doing VC. Maybe with a focus on more promising efforts. Maybe even purely for environmental benefits of using electricity which would otherwise be used for idle machines, although I'm not sure if that actually works out. 
4. One alternative might be to mine cryptocurrency and donate the rewards. (I'm not sure whether that's net positive..).
5. Another alternative is to consider donating directly to scientific research to be spent on other sources of computing (or perhaps advertisements to their VC efforts or something like it).
6.  

Unfortunately, this is unlikely to be an effective use of resources (speaking as someone who worked in high-performance computing for the past 18 years).  The resources you can contribute will be dwarfed by the volume and efficiency of cloud services and supercomputers.  Even then, due to network constraints the only possible tasks will be embarrassingly parallel computations that do not stress network or memory, and very few scientific computing tasks have this form.