Many DBMSes including Oracle do not have a Boolean column type, so this may explain why there is no Boolean field type in ArcGIS either.
@Emily's suggestion of using a coded value attribute domain is a good one and I believe this is the ESRI-recommended best practice.
The only other suggestion I would have is to use a
CHAR field of length 1, as this way you can use the slightly more descriptive "Y" or "N", or "T" or "F", rather than 1's or 0's, and, according to this article, in Oracle 1-character
CHAR columns are actually more efficient than 1-digit