Why did you tag it as javascript?
Scheduled jobs (including report exports) will be visible on the Setup page so that's a screenscraping solution. This data should be also available in the CronTrigger table. As far as I know tis table doesn't support updates so you can only detect them with SELECT, it'd be a manual action to kill them and schedule new jobs with different user.
Data Exports - I think there's only 1 weekly export service possible? Manual check / screenscraping I'm afraid. Or your team of sysadmins will get notifications that the job has failed because the user is inactive.
Workflows (email updates actually) and hardcoded references in code: I'd run a search in Eclipse (or download files with any other Metadata API tool).
Approval processes: this used to be painful, now they're part of metadata too.
EDIT
Have you ever used Force.com IDE? It's a tool targeted mainly at Developers (Programmers) but can be used by System Administrators too. It's capable of retrieving your whole Salesforce project (object definitions, fields, classes, page layouts, workflow rules, sharing rules...) as well as making changes to them and moving them from one environment to another. If you have bigger set of changes to deploy it might be faster to use the IDE than to click through changeset creation. It's essentially a plugin to Eclipse - tool for programmers written in Java.
There are other Metadata API tools available. Depending on to what extent you need to script it at some point you'll probably ditch Eclipse in favor of Migration Tool which will make it possible to run project retrieval from commandline, then you'll probably search for your user with some XML parsers... But for now I'd recommend Eclipse as it's easier, more visual. (Side note: Data Loader could be used for similar thing - to search for all records owned by said user and transfer them to new owner. Metadata is about your config, tables in database etc, not about actual records stored in these tables).
Anyway: download the IDE and click through the creation of new project (this might help, check out at least the images). You will want to download whole content of workflows directory for example. This page with checkboxes will eventually produce for you a master file called package.xml (this file will work exactly same way in Migration Tool). It might have several nodes in it but among others it should contain "workflows".
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<Package xmlns="http://soap.sforce.com/2006/04/metadata">
<!-- Some other stuff, depending what you clicked -->
<types>
<members>*</members>
<name>Workflow</name>
</types>
<!-- Some other stuff (in alphabetical order) -->
<version>26.0</version>
</Package>
Finish downloading (later you can right-click "src" folder to go "Force.com -> refresh from server"). You'll see all your workflow defnitions and have to run search on them. I won't help you with XML parsers ;) But in Eclipse Ctrl+H should bring a global search (Ctrl+F will search only in open file).
Sample workflow definition file (on creation of new record of some custom object it copies the value from Account that was provided in lookup):
<?xml version="1.0" encoding="UTF-8"?>
<Workflow xmlns="http://soap.sforce.com/2006/04/metadata">
<fieldUpdates>
<fullName>Copy_XXX_From_Account</fullName>
<field>XXX__c</field>
<formula>TEXT(Account__r.XXX__c)</formula>
<name>Copy XXX From Account</name>
<notifyAssignee>false</notifyAssignee>
<operation>Formula</operation>
<protected>false</protected>
</fieldUpdates>
<rules>
<fullName>copy</fullName>
<actions>
<name>copy</name>
<type>FieldUpdate</type>
</actions>
<active>true</active>
<formula>ISNEW() || ISCHANGED(Account__c) || ISCHANGED(XXX__c)</formula>
<triggerType>onAllChanges</triggerType>
</rules>
</Workflow>
The workflows you're most interested in will look different. <rules> tag will still be there (firing condition) but you'll probably be looking for nodes with <emailalerts> or whatever is the name, I don't remember.
Consult Metadata API guide for more goodies. For example I can't see it yet in my sandbox as I'm not upgraded to Summer '13 release yet but I know that soon it'll be possible to download approval process definitions. The list of supported types is here: http://www.salesforce.com/us/developer/docs/api_meta/Content/meta_types_list.htm
And page for approval process contains a sample XML that you could prepare your search for.