What is the difference between uilleann pipes and bag pipes?
Bagpipes encompasses all forms of pipes
(did I spell that correctly?)
Uilleann pipes, or Irish pipes as some people call them are native to Ireland.
Check this link:
http://www.hotpipes.com/main.html
ah i should specify,
difference between U pipes and scottish (say highland) bagpipes.
uilleann pipes are typically in the key of D, they are bellows blown (instead of mouth blown), have a sweeter, softer, quieter sound, have twice the range (or more), have drones that lay across the lap of the piper, and three “regulators” which are basically stopped drones with ranks of keys to accompany yourself with chords while playing (they sit on top of the drones). Chanters are commonly set with four or five keys used for accidentals or, in the case of the fifth, the 3rd octave D. Because of the drones and regulators, they must be played while sitting down.
You can see a sketch I did of myself playing at the bottom of my page http://members.aol.com/pipesofireland or go to Na Píobairí Uilleann’s website for other photographs (I just didn’t see any as large as the sketch).
Francis O’Neill quoted one person as saying “The difference between the Scotch bagpipe and the Irish Union Pipe is that the Irish pipes are a musical instrument.”
O’Neill played the Lowland pipes and was an adjudicator at Highland piping competitions, as well as being a friend of many Highland pipers, by the way.
One is Irish the other is… erm Scottish
Liam 
Check out The Universe Of Bagpipes to open your eyes/ears a little bit about bagpipes.
How does he find time to play with all his toys? 
Francis O’Neill quoted one person as saying “The difference between the Scotch bagpipe and the Irish Union Pipe is that the Irish pipes are a musical instrument.”
The other difference is that my cat actually likes the sound of uilleann pipes. She will curl up around my feet as I practise (and practise, and practise …).
On the other hand, any cat with any sense of self-preservation will run at the sound of highland pipes (which have been compared to a bunch of people yanking on cats’ tails). I think the only thing cats fear more than highland pipes is Chinese restaurants (you didn’t really think that was satay beef, did you?).
djm
Don’t forget vacuum cleaners and violin shops!
Anyway, this happens to me too, I am butler, chambermaid, and adopted father to a pair of four-year-old female tabbies (littermates) that don’t mind hanging around while I practice, it doesn’t bother them at all, but they’re used to it, too.
Years and years ago (as a teenager), a neighbor would leave his highland pipes with me to noodle around on while he was on summer vacation from college. I had albums that I tried to imitate; there were no teachers in town that I knew of. I’d go up into the attic to play, and the family cat would eventually show up in the doorway and yell at me. Of course I wouldn’t stop, so she’d walk up to me and start gnawing on my ankle. A contest of wills, it became a dysfunctional formality. 
fertheluvagodandallthatisholy STOP, you great big house ape! [bites ankle] hilarious
One of mine tried to claw my bag but thankfully it is pretty tough and she did no real damage.
A friend of mine was once playing in a pipe band contest, when a small but exuberant terrier charged out the crowd, leapt up, bit, and held onto the bell of his chanter.
With fortitude and presence of mind, he shook the dog off the chanter, then booted it over the head of the pipe-major. To the best of my knowledge, dogs have left him alone ever since.
Something similar once happened to the great Willie Ross during a piobaireachd contest; however, it turned out that the bootee was owned by the presiding judge. No prizes that day.
Oh, my friend’s band won, by the way.
Cheers,
Calum
speakin of cats and pipes, my cat tansy will get up from a deep sleep to come sit at my feet whilst i plays. often she will kind of sit and lean her head-cheek against the bass drone U bend. of course she was raised right, on a sailboat with whistles and pipes from birth 
when highland pipe drones are playing by themselves without the chanter, it sounds remarkably like a leaf-blower. On the uilleann pipes, this sounds more like a 3-octave split on a lovely little reed organ. Highland pipes are in a non-existant key (somewhere between Bb and B natural) and for some reason the music for it is in A, WTF? Uilleann pipes are most commonly in the key of D, and D means D, concert pitch, you can actually play with other instruments, WOO HOO! Highland pipes are taught through stict, annal, limited, and artistically bastardizing learning regiments. Uilleann pipes are commonly used as a tool for artistic expression. Highland pipes are as loud as a semi-truck horn. Uilleann pipes are in the nice volume range of a fiddle or accordion (depending on bore size/reed strength etc.) These are the primary diferences that i can see.