Across the internet, and especially among academics and internet savvy users (which include many scientists) there are growing "open information" movements. One which is of special interests to scientists is the "Open Science" movement, which seeks to help facilitate scientific discussions in a way that helps promote productivity and fairness, while also bringing a more immediate transfer of information.
The Open Science movement has largely developed in opposition to the gatekeeper status of the peer-reviewed journals, which many scientists view as an archaic and costly way of providing scientific scrutiny.
Open Science is the catch-all term for attempts to provide scientific research information in an open way. It's an umbrella term which includes Open Notebook Science, Open Access/Open Information/Open Data as it relates to scientific works, and sometimes even Open Source.
Part of the reason for the Open Science movement is to get the information out for scrutiny and comment by the scientific community in a timely fashion.
Open Notebook Science
Open Notebook Science is an extremely comprehensive form of Open Science, which believes that every bit of data - the entire "scientists' notebook" in fact - should be available for scrutiny by other scientists. Some scientists advocating this approach believe the data should be available in real-time, so that literally the data would be available for others to analyze while the scientists involved may still be working on the actual experiment. Others believe that it would be appropriate to have a time delay, so that early drafts of proposals and papers, for example, could be developed by the scientists responsible for the research before the information is made available to the general public.
Open Data is also known as Open Information, and is the practice of making data publicly available, without invoking copyright or other restrictions.
Open Access is a practice, often in academic publishing such as peer-reviewed journals, of making all published papers freely available to the public. Many scientific journals allow the authors to publish preprints of their articles available online for free, most notably on the arXiv.org website. Though definitely a positive step, this is still seen by many as insufficient, because it keeps the peer-reviewed publishers in the role of moderators of scientific content.
Open Source is the term originally utilized by computer programmers for a program in which the code was publicly available to be reviewed and modified by any programmer who wished to do so. The most well-known successful case of open source software is the operating system known as Linux, which many programmers consider to be far superior to the proprietary systems on the market (like Windows).
The phrase Open Source has migrated out of the computer world, however, and it's not uncommon to hear it applied to other sorts of design processes, such as architecture.
Citizen Science is a phrase which describes a scientific research effort to include non-scientists in the scientific process. Individuals with little scientific background can often join in these efforts to . One example of a citizen science program, which includes active participation on the part of the non-scientists, is Galaxy Zoo, where non-astronomers can classify galaxy images by type. (The program has proven so successful that the creators have expanded to an entire Zooniverse of such projects!)
While open science could help support citizen science, by given non-scientists greater access to scientific information, it is important to realize that a citizen science project does not necessarily result in an open science outcome.
Crowdsourcing results from a mash-up of "crowd" and "outsourcing," and represents the idea of a group of people working together on a project, to utilize the benefits of mass collaboration (not to mention sheer volume of workers) to reach a desired outcome. (The Galaxy Zoo project, mentioned above, would be one such example of this, as well.)
Though open science methods help facilitate crowdsourcing, it is certainly possible to have a crowdsourcing situation which does not result in an open science outcome.