In Japan, we don’t have the custom of celebrating Christmas since the majority of Japanese people are not Christians.

In December, we are busy preparing for our most important, traditional event/festival “New Year’s Holidays”, and there are events to look back at the previous year.

Unlike annual results, this year, there were three words relating to politics in the top 10 words, which shows that we cannot talk about the Japan of 2009 without the change of administration and the new government’s policies. (I am not sure if you mean previous years' results here?)

The new government, in order to review the entire national budget, held an open meeting for 9 days, and the meeting ended only a few days ago.

The bureaucrats and other people who are in charge of projects answered the questions asked by the members, who had been chosen by the government.

They also had to deliver effective presentations to persuade the members to admit their budgets applied within an hour. (Again, not quite sure what you wanted to say here. Do you mean "persuade the members to authorise/back their budgets in no more than an hour-long presentation?)

Anyone was able to watch/view the meeting at the meeting (web?)site and through live blogs. (Without 'web', you would probably want to say 'location', as in 'meeting location' or 'meeting venue'.)

Although the meeting is controversial among specialists, politicians and the other people involved, it’s been reported that the majority of the public show a favorable attitude toward the open meeting.

It’s true that the meeting led to many people becoming more interested in how, and for what, their taxes have been used.

In Western cultures, people might be busy preparing for Christmas.

The former is one of the campaign slogans used by a remarkable politician.

In Western countries, many people are already preparing for Christmas. ["Might be busy" sounds odd to me. Perhaps you mean that some people are, although not everyone. I'm sorry if I misinterpreted your intent.]

In December, we are busy preparing for our most important, traditional event/festival, the “New Year’s Holidays”, and there are events to look back at the year. [The phrase "events to look back" feels awkward to me, but I can't think of any reasonably brief phrase to replace it. I want to say something like "... there are various ways in which we focus our attention on the events of the year which is coming to an end."]

Unlike the results in previous years, this year, there were three words relating to politics in the top 10 words, which shows that we cannot talk about the Japan of 2009 without discussing the change of administration and the new government’s policies. [The phrase "the policies of the new government" sounds slightly better to me.]

The other two words relating to politics were 脱官僚 (debureaucratizing or debureaucratization) and 事業仕分け(project classification). [Either "are" or "were" is possible, but this should be consistent with the verb choice in the previous sentence, at the phrase: "...this year, there were three words..."]

The former was a campaign slogan used by a remarkable politician.

The latter is a very hot phrase. [I am assuming that this is a newly invented term. As such, it is in some sense not an existing "word" of the language, but a phrase consisting of two words which has acquired a new and specific meaning. In English, since we have word breaks, there is a sharp distinction between words and phrases. It is hard to say which is the better way to refer to a newly coined compound in Japanese when speaking of it in English.]

The new government, in order to review the entire national budget, held an open meeting for 9 days, and the meeting ended only a few days ago. [I vote for the comma which Martyn-san crossed out.]

Among about 3000 taxpayer-financed projects, the government first picked out 477 projects in which there were uncertainties and the need to review their budgets.

The bureaucrats and other people who are in charge of the projects answered the questions asked by (the) members of the meeting, who had been chosen/selected by the government.

They also had to deliver effective presentations within that hour to persuade the members to approve their budgets.