Poster¡G Lynx at 22:29:57 3/15/98 from h204.s13.ts30.hinet.net
In "Ozymandias," the dramatic irony is that although Ozymandias was once king of kings, the sculpture of him would also sank in the sands. We can imagine he was powerful when he wasn't old. The 4th and 5th lines may reveal the aged power-lost condition of the king. After death, a sculptor that might have less respect towards him, resulting in the fact mocked his appearance that his sculpture was made old. 
According to the words on the pedestal, the king was proud of his works. It's possible that he did make it, so he was great enough to have a sculpture left behind. However, the sculpture was going to vanish in the sands, which stands for that his great works would be forgotten. 
In a sense, one's value should not be judged by others' opinion but his own. As for Ozymandias, if he thought his value was depended on other people, he lost all his value because there was nothing and nobody surrounded his symbol of great works. Such natural things as sands were also viewed as a rub to the maintenance of his reputation in his view. 
In the 2nd stanza of "Ode on a Grecian Urn," the first line "Heard melodies are sweet, but those unheard are sweeter" may reflect the piper was piping for the girl, and his words towards her. The piper is not like the bold lover: he couldn't speak aloud. 
In the 3rd stanza of this poem, the first 7 lines show the happiness of love. The boughs cannot shed their leaves may symbolized the lovers cannot leave each other or can't have no concern on each other. The last three lines show that the exciting affection could vanish one day, soon or late. 
The 4th stanza presents the little town is empitied, and there's not a soul after the heifer was sacrificed to the altar. The altar is the destination and can be a symbol of a goal; the heifer can be one of the principles. I think one can't lose one's principle to achieve a goal, or he will be an empitied person. 
The last stanza makes me think about what beauty is. Be overwrought things as marble brede or trivial things as branches and weed? Is happiness beauty? Is woe? Whatever is true is relative beauty, in my opinion.