Yes.  Get the "WTK" from Sun for fairly generic ones.  Nearly all mobile
phone vendors also have their own emulators that let you try out
features specific to their phones.  These can be embedded into
development environments (e.g., see EclipseME), but can also run stand-
alone.

As someone else said - try the WTK (wireless toolkit) from Sun.

Beware - something working fine in the emulator on your desktop is no
guarantee it will be happy once it gets onto a phone!
In particular, be aware of threading issues - you can't hog the
processor at certain points (e.g. startApp), or most phones will sulk -
you have to spawn off a thread and return immediately.
Also, different phones have different 'quirks' (a bit like web browsers
then!).
lex