Derived from yug (युग)+ aadi (आदी), it means beginning of a new era. It isbelieved that Brahmaji (ब्रह्माजी), the creator of the hindu pantheon, started creation on this day - chaithra shudhdha pratipadhe. Also thegreat Indian Mathematician Bhaskaracharya's calculations proclaimedteh Ugadi day from the sunrise on as the beginning of the new year, new month and new day. It marks the beginning of a new hindu lunar calendar with a change in the moon's orbit.
People eat neem (नीम) and jaggery (गुड़ ) on this day. Neem has a bitter taste while jaggery is sweet. The significance being that one should be as sweet as jaggery to others and that life is a mixture of good and bad, joy and sorrow, and success and failure; but one should take everything in one's stride in the coming year.
The traditional food for this festival is "holige" (होलीगे) and "puliogare" (पुलीओगरे or tamarind rice).
My menu: sewiyan payasam (सेवियाँ पायसम) and ambude (अम्बोडे). I found a cool kolam site। It has a flash demo of how to draw the kolam. It doesn't have too many designs though. I made the "diya" kolam.