I'd say that was a pretty reasonable weight, certainly if you built it on a budget. I doubt there's any single place you could lose a big chunk of weight (unless you've got an unusually heavy frame or wheels) - it's usually just little amounts off everything that makes the difference between what you've got and a (say) 18 lb bike.
My lightest bike (fast tourer/audax, Mercian 531 frame with Campag Centaur/Chorus/Record mixture) weighs a bit over 22lbs with luggage rack and mudguards, which I think is quite good for a "non-race" bike. But it's also relatively expensive (probably cost something like £2500 to replace with new parts). In 2006 I had the frame refurbished (was new in 1990) and rebuilt the bike with road/race components rather than the old mix of MTB and road stuff (I used to use it for heavier touring). That dropped around 3 lbs from the overall weight, but using lighter wheels (OpenPros instead of the old touring rims) made a big difference to the feel of the bike. I'd say it "feels" pretty much as fast as some much lighter bikes I've ridden.
I wouldn't worry so much about total weight, but definitely look at the wheels as the first area to upgrade/throw money at - makes the biggest difference to the riding experience, rather than just a number to quote at people.
EDIT Just seen your other post - I reckon you've done pretty well for the money. Lose the flat bars though!!!