I'm trying to set up an 802.1Q VLAN trunk between gigabit ports on an HP ProCurve 5300XL and a Cisco Catalyst 3548. Can anyone point me to some configuration examples on how to do this? Thanks!

Wouldn't that be nice to have. Guidelines when connecting competitor hardware... :-) Having done it recently dealing with HP to HP and HP to Nortel there are some pitfalls. It all comes down to tagged or untagged. A uplink trunk on the Nortel could only be one or the other. We had to provide a second trunk to the HP switch [as tagged] and then associated ports with that vlan [untagged]. The Nortel could do multiple vlans on one trunk but we would have to configure all ports on the Nortel as tagged to do so. Too many connections and downstream switches to make this viable. Hp to Hp allows you to have both tagged and untagged on the same trunk so we tagged the trunk for the vlan [as well as untagged for everyone else access]. Then associated ports at each end for the vlan as tagged. You will have to figure out the Cisco part. It took some reading and playing to get all of this to work but it works well and no hiccups.