I have recently worked with a group that wished to add a timetable for a village hall to their site. It is important to appreciate that where possible you do not want to have multiple data sources containing the same information, and where this is a necessity, then there is only one primary source that everything else is derived from. (The website should not be your primary source for data in case you lose your site!)
In this case we found that simply copying and pasting the table from MS Word into the WordPress editor basically worked. However not all formatting in MS Word is carried over. It is also wise to erase as much formatting as possible because MS Word used to bring a lot of formatting information across which wasted a lot of bandwidth.
When you look at the resultant table there are some quick formatting things you can do to make the table more user friendly. The tutorial and an example table are included in the following documents.
The first document is in PDF format, the second document is in MS Word format. You only need one or the other.
Adding tables to WordPress (PDF)
Adding tables to WordPress (MS Word)