btw, you might want to check into this: you can consolidate a
particular loan once--not just go through the process once.
That means, consolidate now, then consolidate 5 more loans years later. Perfectly legit. The previously consolidated loans are just fine but a seperate event.
Unless I'm on crack, but my undergrad loans are all consolidated under last years extremely low rates. Also, the place I went through drops another point off after 3 years of payments. Check into special incentives like that, too.
There are a lot of ins and outs to consolidation (like repayment plans, default options, losing certain rates and forgiveness tiers, for example). You might benefit from a visit to your local admin office, mainly because I don't want to dig out my paperwork and type it all out

sorry 'bout that.
EDIT: oh what the hell, I'll give some of it a shot from memory:
ok. short of it is, you want to consolidate. That's not an issue in my mind--you can consolidate your later loans again, just not the ones you consolidate now, which isn't an issue because the rates won't ever be lower again in your school lifetime.
But HOW?
ok, so you might have some loans that can be forgiven, say if you are going to be a teacher or nurse or something along the lines listed in your Perkins package. You likely don't want to consolidate those since they won't be able to be forgiven once you do.
Also, your old loans were given to you at, what, 7%? and your newest ones were like 4%? You don't get the rock bottom for all of them--it's a weighted average. So you have to decide whether it's best to go with an overall 5.55% (for example) or, if you only have $2K at 7%, just pay it off and consolidate the 4% straight through. You see how that works? But maybe you have $5K at 7%, so drop the whole whammy in.
You have to sit there and play with the whole thing until you come out with the best option for yourself.
I think what my wife and I did was to NOT consolidate our perkins (5%) because we only had like $2K and they were subsidized while in school (or maybe just low enought principle that it wasn't worth it to raise my overall consolidated rate). Just pay those off quick. I dumped my unsubs into a locked rate, left half of her oldest ones out, added my newest ones together and viola:
approx. $2K at 5% and the rest at 3.5% (hers just dropped to 2.5% after the 36 month deal). My unsubs are sitting at approx 4.75% or something and my newest ones (unconsolidated) are coming in at whatever rate is now.