As for the relationship between Muhammad bin Abdul-Wahhaab and Ibn Taymiyah, Abdul-Wahhab was indeed influenced by Ibn Taymiyah. In fact Abdul-Wahhab started a similar movement at his time. But Abdul-Wahhab had his da3wa (invitation to Islam) in the heart of the Arabian Desert, while Ibn Taymiyah in the center of the area and heart of Islam at that time, Sham (Syria). So he gained much more followers.
Muhammad Bin Abdul-Wahhab came at a similar time, when in Arabia people started worshipping stone and grave in the name of Islam. He fought a lot of innovations and additions to Islam and his efforts succeeded in uniting with the family of Sa3ud and forming the first Saudi state, but at that time the family of Saud were righteous people, unlike the family of Saud of today. It is interesting to note that Abdul-Wahhab and his students were all Hanbalis, just like Ibn Taymiyah. The first Saudi State ended with the 3rd Ottoman campaign led by Muhammad Ali Basha himself, but even that failed to erase the methodology. The methodology is until today widespread in the entire peninsula and not only Saudi Arabia.
Frankly, I hear a lot of slander thrown at Muhammad bin Abdul-Wahhab, and I personally used to dislike him. But when I read his book Kitab al-Taw7eed and checked the accessions thrown at him I did not find any of the slander thrown at him truthful. Some cases he is clearly innocent from what is said, sometimes what they accuse him of is clearly in accordance with Quran and Sunnah. Like for example the Sufis attack him for destroying the dooms that were built over the graves of the Companions, but the fact is there are many Hadeeths that say that such things are the actions of the Jews and Christians, and that those who build such things are the worst of the creation and that the Prophet cursed such a thing, and that he strictly forbade such a thing. So as you see, those who attack him are either ignorant about the Sunnah or are just venting out hatred against Arabs.
Some of the other innovation Abdul-Wahhab students canceled, was the innovation of performing four prayers one for each school (mathab). Like a Hanafi would do Athan (call prayer) and then all the Hanafis would perform the prayer behind a Hanafi Imam, then a Maliki would do Athan and the Malikies would do their prayer and so on. Abdul-Wahhab students canceled this and praying in the Ka3ba returned to be unity like it was at the days of the Companions and like it is today, thanks for Allah.
In fact if Abdul-Wahhab is what I know about him by now, then he is Insha' Allah another reformer (Mujadid) like Ibn Taymiyah: he revived the forgotten of the Sunnah, he fought innovations, and he returned the people to the understanding of the Companions.
As for the Wahhabi Da'wa today, most Wahhabi people live in Saudi Arabia. Almost all people in Mecca and Medina belong to this school. They don't use the term Wahhabi, but rather, Salafi Da'wa or Ahlul Sunna wal Jama'a. Although, they have a negative view about women and some modern inventions, they played in important role to keep Islam alive in Arabia. They also played a significant role in raising up Islam and resisting missionary Christians in the Muslim world. Many people think that Wahhabi people are bad because the King of Saudi Arabia is bad. This assumption is clearly wrong since the Saudi king does not follow that school. His jails are full with Wahhabi scholars. Some people (unfortunately) slander Wahhabis as a way to slander Arabs. If you want to know the truth about those people, I advice you to check this site that is maintained by a famous Wahhabi scholar: www.Islam-qa.com and check out www.usc.edu/dept/MSA
Ultimately, I advice all Muslims: Do not judge people before you listen to them.
See also: [An Introduction to the Salafi Da'wah] [What people think of us]