A small number of people may gather in a fancy building, on a street corner, in a coffee house or library, or on the telephone (or yes, on the internet) for worship, praise, and service. Of course, that's the promise of this verse.
It's important to take this verse from Mt 18 in context, though. It comes right after the verses on church discipline, where Jesus urges people to use appropriate means to cope with disputes, avoiding making a big public deal about things that can be handled faithfully by a small number of people.
As is often the case with things Jesus says, there's a streak of radicalism here. Jewish tradition and practice calls for a minyan -- a gathering of ten -- for prayers. Here is Jesus, in the Gospel written for the Jewish community, saying two or three is plenty.
Finally, @Mason Wheeler made a good point. Please don't mistake Christianity.SE for a congregation. If you don't have an in-the-flesh congregation, please consider finding one. Christianity is most definitely an in-the-flesh religion and spiritual path.