I may be doing a few posts here and there about a few applications for the iPod touch. But, I want to add information that will make these posts helpful, so expect each one to have a few examples, if possible. In the least, I hope to describe at least 1 missing feature you might find important.
First, Apple for some reason did not include the ability to search LDAP servers into the iPod / iPhone Mail application. A horrible omission for someone who’s used to having To: field searches available at his fingertips. So, what to do? Well, you could use an online search (if your organization has one) via the web, or you could look for an application. I looked for an application. I found: LDAPeople by Neoos Software. 
To read about how to setup LDAPeople for the UIUC Campus, and more about it’s interface etc., click “more”…
LDAPeople is a simple application that opens to a simple search interface. Type in a name, hit search, and you get a list of returns from the server. Click it, and you get the information that is parsed by LDAPeople into a Contact app card (which can be added to the Contacts application right on your iPod right away). Of course, when you sync, if your settings are set up in iTunes properly, it will also add this contact to your Address book on your mac etc.
This is great. So, that solves the problem of writing e-mail you know needs to go out to Person X (Mr. Fawlty above, say for a hotel room), but don’t know his company e-mail address.
You need to set up the client with information regarding your organization, and in order to help those on the UIUC campus, here is the info I use in LDAPeople to facilitate searches on campus. [I'm working on fixing a few problems with this, but you should find a few items helpful...]
Basic Settings:
Server: ldap.uiuc.edu
Base DN: dc=uiuc,dc=edu
Bind DN:
Password:
That’s the basic stuff- similar to what is used in Thunderbird, or Mail.app to get LDAP search working on campus. [See Cites website for more info on that.] But, the more advanced settings can prove helpful for your searches on campus. In particular, pay close attention to the Filter Line. (all one line on the pod). In LDAPeople, % is a wildcard that means anything you type in the search field. %1 is the first word, %2 the second etc. So, the line below searches for any instance of the total search item in the given name (first name), or the surname (sn), also searches for the first word in the givenName field, and second word in the sn (surname) field. Finally, it also searches for the campus user ID (uid) which is your uiuc username. This can be very helpful if you remember the persons UID but need to call their office for instance. Drop their UID in the search field, and check out the LDAP results. [Interestingly, it gives all UID's that start with that string... so if you keep getting e-mails from someone with a userid of "yourid2" or something, when yours is "yourid" this could help you find who the heck they were trying to e-mail.
Advanced Settings:
Sizelimit Warning = ON
Filter: (|(|(|(givenName=%*)(sn=%*))(&(givenName=%1*)(sn=%2*)))(uid=%*))
Selection: givenName sn uid
Base Filter: (objectclass=*)
Search Scope: Subtree
In order to make up a Contacts app contact card, some attributes from the LDAP server need to be "mapped" to attributes in the Contacts app card. This is my attempt at mapping more useful items into the contacts card in LDAPeople for the UIUC campus. Note that uiucEduMiddleName and uiucPersonNickname give you what they say it does, and adds them to the contact card. [Can be useful for people who's names differ significantly... say Cynthia -v- Cindy.] Right now, I don’t believe there are any jpgPhotos stored in the UIUC LDAP server (but I didn’t spend a long time on this today, so I can’t be sure).
Attribute Mapping:
First Name: givenName
Last Name: sn
Middle Name: uiucEduMiddleName
Name Prefix:
Nickname: eduPersonNickname
Organization: o
Job Title: title
Department: ou
Note: uiucEduText
URL: labeledURI
Picture: jpegPhoto
A few additions to Phone Attributes helps to find their basic numbers if needed to get a hold of them at home. Please be aware that if you aren’t on VPN or WPA2 on campus (does VPN even work on campus for the iPhone?!), you won’t get some of these numbers- they’re only available within the uiuc.edu domain. Of particular note is the uiucEduUserEmailAddress line which should populate a gmail or yahoo account etc., if they have added it to their information. [This is available off campus.]
Phone Attributes
Mobile Phone: mobile
Phone Work: telephoneNumber
Phone Home: uiucEduHomePhone
Phone Other: uiucEduOtherPhone
Phone Work FAX: facsimileTelephoneNumber
Phone Home FAX: uiucEduOtherFax
Pager: pager
E-mail Attributes
E-mail Work: mail
E-mail Home: uiucEduUserEmailAddress
E-mail Other:
Address Attributes is not perfect right now- it doesn’t populate the street, city etc.- probably due to my lack of knowledge of LDAP. But, it does make a line that could be used by a human to send a letter, etc. if needed. Can be useful.
Street Work: postalAddress
[...]
Street Other: uiucEduMailingAddress
So, there you have it, some alterations to LDAPeople settings that hopefully prove useful to at last 1 other person on campus. 
Oh, LDAPeople is not free, it’s currently $1.99 in the iTunes store. I’ve used it a bazillion times already, so it’s already paid for itself in usefulness.