It depends on if you plan to celebrate the festivals within the land of Israel or outside the land of Israel. Historically and presently, in the land most festival Sabbaths are celebrated for only one day and outside the land, all festival Sabbaths are celebrated for two days. Historically Rosh Hashanah was celebrated for two days in the land as well as outside of the land even when the Temple stood for obvious reasons.

While it is permissible to work the intermediate days of the festival of Pesach and Sukkot, it is traditional to do the least possible. However if you work for someone, do not enter into theft by being lazy or appearing lazy!!! If you can get reduced hours or use your vacation days for those days as well that is optimal. Most will not be able to do that because of employer needs and a lack of Torahfulness within the Diaspora in general (our society works hard at making any level of obedience and celebration of Torah as difficult as possible.)

These are the dates that are kept according to the ruling of the Sanhedrin in the 4th century CE for those outside the land of Israel.

See the discussion: Moedim 2008 (Feasts & Holidays)

Pesach

1st seder April 19th in the evening Also begins first festival Sabbath
2nd seder April 20th in the evening Also begins second festival Sabbath
Days needed off from work (April 20th and April 21)

7th day of Matzah April 25th in the evening Also begins weekly Sabbath
2nd - 7th day of Matzah April 26 in the evening
Days needed off from work (April 26 and April 27)

Because of having the festival Sabbath follow a weekly Sabbath, it will be beneficial to have Friday April 18th off for cooking, final cleaning, Pesach preparation, etc. For a complete schedule for Pesach this year I have attached what I have posted on our web site. It includes how to prepare and suggestions as to when to begin each step of preparation for Pesach. While It is not as comprehensive as I would like it to be, it provides a good starting point for most in regards to preparation.

See Article: http://www.jerusalemcouncil.org/pesach-2008-5768.html

Shavuot

1st day of Shavuot begins evening of June 8th
2nd day of Shavuot begins evening of June 9th
Days needed off from work (June 9th and June 10th)

Rosh Hashanah

1st day of Rosh Hashanah begins evening of Sept 29th
2nd day of Rosh Hashanah begins evening of Sept 30th
Days needed off from work (Sept 30th and Oct 1st)

Yom Kippur

1st day of Yom Kippur begins evening of Oct 8th (begin fast also)
2nd day of Yom Kippur begins evening of Oct 9th (not traditionally fasted)
Days needed off from work (Oct 9 and Oct 10)

Sukkot

1st day of Sukkot begins evening of Oct 13th
2nd festival Sabbath of Sukkot begins evening of Oct 14th
Days needed off from work (Oct 14 and Oct 15)

Shemini Atzeret

1st day of Shemini Atzeret begins evening of Oct 20th
2nd day of Shemini Atzeret begins evening of Oct 21st (also begins Simchat Torah)
Days needed off from work (Oct 21 and Oct 22)