can use following items:
1) XPDL in jawe; for objectweb
2) JBoss workflow(JBPM)
3) Oracle BPEL

I can suggest for U to use the JBPM engine  it has a very powerful langage the JPDL so you can envisage Human interactions and automated actions or the timer provided by the core and so...
It's a very nice engine made by the JBoss community and i'm using it in my project of end of study.

But human interaction  in these engine  is not supported
with other engine

there are two options:
standard based workflow  engines
non standards
there are various standards for workflow, the best one is from
wfmc.org and the worst is bpel.
if the workflow will be used only internally standard  based workflow
engines are very limited. you may use other engines which have their
own language  and design idea.
jBPM from jboss is one of those you can find several others by a few
search in google and other search engines.
serveral of them are hosted on source forge.
if your customer is in iran you can also user commercial procuts which
are likely much better than most of their open  source counterparts.

workflows are different things from bpel engines !
their usage is also different !
you use bpel engine  like pxe in integration projects when you want orchastrate services . but workflow  usage is in situation when you want for example implement automation in process  level in a organization that involves human interactions ! ( BPEL does not support  human interaction  )
after all my suggestion is openwfe or jbpm . Don't go with xpdl standard  in this area because as you know wfmc standard is not a complete one ( surely one of the reasons that some open  source projects like jbpm and openwfe use their own way in this area is the lack of good standard ! they say that xpdl is an incomplete one ! ) .

I agree that BPEL is <<currently>> not workflow. And that's why I
called it the worst standard.

But some people behind BPEL at Microsoft, IBM, BEA and oracle believe
that their invention will become the future standard  for workflow.

Currently most of people refer to BPEL as web service orchestration
standard or web service composition language.
IBM extension to BPEL implemented in Webshpere App Server supports
human interactions, some (including IBM it self) are trying to address
this via more standard ways like BPEL-J or JSR 207.

Any way currently BPEL has much stronger support  than WFMC standards,
specially from the time SAP (First implementer of WFMC standards) has
shifted from XPDL to BPEL in its netweaver platform.

BPEL is considered as way to define business  process and it will
become a workflow  standard in future.
BPEL currently has 3 major problems:
1- human interaction
2- sub process
3- the underlying theory (Pi calculus)

Some people believe Pi calculus is a much found  theory to define
business process. So they don't bother them self with it much but for
the other two there are some work underway:

BPEL4People
Human user interactions – as known from existing workflow engines
www128.ibm.com/.../ws-bpel4p\
eople/

BPEL Subprocesses
Based on a coordination protocol
www-128.ibm.com/.../ws-bpels\
ubproc/

And at last
If any one has read this message to the last we are developing a
workflow engine  in our company and searching for talented software
developers if you are interested in working with us on this subject(of
course with all benefits of a good job) send me your resumes.

Regarding previouse email I want to list all users from my active directory in a java program. but I dont know what would be the parameter to call list method . i am geting

javax.naming.InvalidNameException

which shows I am not using correct name for my context.
does anybody know about that?
try {
.
.
LdapContext ctx = new InitialLdapContext(env, null);
String filter = "(&(sn=Geisel)(mail=*))";
NamingEnumeration answer = ctx.list("CN=Users", filter, ctls);
.

Basicly I am writing a program in java to list all users from active directory and email them. what mail.jar file you think would be suitable to do this?