HP ProLiant Resources

Your tools of trade if you're working with HP ProLiant 3xx+ hardware. I've only got DL360s, DL380s and a few DL320s here at work, so can't say anything about the bigger ones. 

HP SmartStart or Firmware Update CDs
You should know them. SmartStart usually comes with the server, but hp.com obviously has newer versions. SmartStart comes in handy when configuring complex RAID stuff (more than one logical drive per array, something you can't do from the rom-based tool). Fimware maintenance CDs are one-shot firmware upgrades for your machine, so get them from hp.com too.
Yep, you can PXE-boot those. This HP-ITRC forum entry has the details including an awesome PDF 
(local copy of awesome pdf).

My recommendation: have both CDs on your boot server (and in your toolbox), but don't rely on the firmware update being functional when booted from the network - I saw problems when the NIC firmware got updated. Also I had problems with NFS with Release 8.20, but CIFS worked fine for me.

Also, keep copies of the older CD versions, if you've got older hardware. HP sometimes drop support for older hardware from newer CD releases. (Space constraints, etc.)

QuickSpecs: Hardware Specifications
Bookmark the QuickSpecs links for your hardware. Need to know exact physical dimensions? Maximum RAM module count? How RAMs need to be installed for your required RAM configuration? That one box is maxed out on CPU and you need to find faster CPUs? QuickSpecs have the answers. 
Google knows them all

Proliant ILO2 Hardware Health Monitoring using Nagios
See this insidesystems.net blog article

IT Resource Center
Hosts Warranty Check, KB, Support Case Manager. You will need one of them at some point.
HP ITRC Homepage
ITRC logins are not the hp.com passport, so one more login to save.

Care Packs / Hardware support / Parts replacement
Care Packs are warranty extensions. And sometimes also software support.
Lookup tool for your hardware: Here. IE only. Doesn't work sometimes. Have hardware Part and Serial number ready.
If your product is wrong in their database, mail them, they can fix that. (I had an MSA60 recognized as a 6412 enclosure.)

Your hardware QuickSpecs tell you about the included warranty (for most Proliant models this is 3Yrs 9x5 NBD by now), and what Care Pack options are available.

Also, when contacting HP always have your hardware P/N and S/N ready, you'll need them. Sometimes you will also need the purchase date and (maybe) a copy of the invoice (mostly only if you are approaching end of warranty period). Best to document all of this when you deploy the server for the first time.
Store your HP customer number in your documentation. Saves you quite some time on the phone.

Another time I'll talk a bit about the basic software components that ship with ProLiants.