CPLR § 5701

Tomorrow's Law Jounal (online today), has a great article on CPLR § 5701(a), the provision of the CPLR that sets forth those appeals to the appellate division that are available as of right.  The authors, Thomas R. Newman and Steven J. Ahmuty Jr. focus their article, not on the grounds available, but the limitations of those grounds. 

Classes of Orders

CPLR §5701(b) sets forth the following three classes of orders not
appealable as of right: an order which (1) is made in an Article 78
proceeding against a body or officer; (2) requires or refuses to
require a more definite statement in a pleading; or (3) orders or
refuses to order that scandalous or prejudicial matter be stricken from
a pleading.

Even where an order is not appealable as of right, CPLR §5701(c) grants
the would-be appellant the right to seek permission to appeal from the
judge who made the order or from a justice of the appellate division in
the department to which the appeal could be taken, upon refusal by the
judge who made the order or upon direct application:

There are, however, some significant limitations on the right of appeal which practitioners should be aware of.

No appeal lies from an evidentiary ruling made during the course of
trial or from an order on a motion in limine adjudicating in advance of
trial the admissibility of evidence;²
one can argue, without success, that such an order "affects a
substantial right" of the litigant to present his or her best case or
to hamper the adversary from doing so. This is so, even where the
motion is made on papers and the court enters a written order to
provide the aggrieved party with an appealable paper as "a vehicle for
appeal."³ The ruling "constitutes, at best, an advisory opinion which is neither appealable as of right nor by permission."⁴
The provisions of CPLR §5701(c) for obtaining permission to appeal from
an order not appealable as of right "were not intended to permit
intermediate appeals from evidentiary rulings during trial," as to
allow such appeals "would interfere with and impede the trial process."⁵
Moreover, the ultimate rulings during the trial may well depend on the
status of the record at the time the particular evidence is offered.
Therefore, evidentiary rulings, whether made before or during trial,
are only reviewable after trial on an appeal from the final judgment.⁶

Similarly, where an unsuccessful motion for a mistrial is made during
the course of the trial, it is not appealable, even if the ruling is
embodied in a written order. It can only be reviewed on an appeal from
the ensuing judgment entered after trial.⁷
Other nonappealable orders include an order denying a motion to
preclude a plaintiffs' expert witnesses from testifying at trial or,
alternatively, to subject them to a Daubert hearing.⁸ This is, in effect, an evidentiary ruling and, as such, neither appealable as of right nor by permission.⁹
A ruling by the court prior to trial as to what factors the jury should
consider on the issue of comparative negligence would be an advance
ruling on the court's charge and, at best, a nonappealable advisory
opinion.¹⁰