The most popular is probably Disting, primarily celebrated by Ásatrúar, but observed by many other Heathens as well. A tradition that has survived in Sweden since before recorded history, it is now a market, but according to Snorri Sturluson in the Heimskringla, it originally had many other functions as well. Held in Uppsala, also the location of a great Heathen temple, it also coincided with a Swedish celebration of Dísablót, a celebration of female ancestral spirits. Today, it has become customary for Swedish-based Heathens to honor their Dísir (the female ancestral spirits) around this time, and many Ásatrúar celebrate this holiday as an anticipation or welcoming of spring. Snorri also states that the date of this market had been changed to Candlemass, which is how we know to celebrate it at this time.
In his book Travels Through Middle Earth: the Path of a Saxon Pagan, Alaric Albertsson writes about an Anglo-Saxon holiday called Ewemeolc, meaning literally "ewe's milk". He posits that it comes from the similar Celtic holiday of Imbolc, and gives ideas for celebration that are quite similar. In looking for historical sources that talk about this holiday, I was unable to find anything - though that certainly doesn't mean there aren't any!
Personally, as an Anglo-Saxon Heathen, I celebrate the Charming of the Plow in February. The Venderable Bede writes in 725 in his De Temporum Ratione that Solmonath (around our modern February, see more calendar info here) can also be called the Month of Cakes, because the Heathens would offer cakes to their Gods in that month. It directly translates as "mud-month", which many have speculated is due to newly-plowed soil combined with the typical English rains. I have written a Paganized version of the Æcerbot, a ritual recorded in England in the 11th century that my children and I perform in our own garden on this day - including some offerings of cake! I celebrate it on the first full moon in February, based on the idea of the Anglo-Saxons having a lunar calendar in which months begin on the new moon - this year, we began at sunset on the 13th and celebrated through the 14th. The Charming of the Plow is not limited to Anglo-Saxon Heathens, though - many Heathens celebrate this same idea, though non-AS practitioners will probably not borrow so heavily from the Æcerbot!
And that's just the Heathen holidays I'm aware of in February! Unlike Imbolc, which has a pretty standard spring-milk-Brigid celebration structure for many Pagans, Heathen holidays around this time of the year are incredibly varied, and have many different purposes.