What are some quotes from Hamlet that prove Hamlet and Ophelia's love for one another?

When Hamlet learns that Ophelia has died and that it is her grave that the gravedigger he's been bantering with is digging, he clearly feels great grief.  When Laertes, her brother, jumps into her grave to hug her one more time, Hamlet steps forward, reveals himself, and insists that he loves Ophelia more than Laertes does.  He says, "I loved Ophelia. Forty thousand brothers / Could not with all their quantity of love / Make up my sum" (5.1.247-249).  In other words, Hamlet says that his love is so much greater than Laertes's that even if there were 40,000 brothers to love Ophelia, Hamlet's love would still be bigger. 

Further, Hamlet wants to prove how much more he loves Ophelia than Laertes does, and he says that he's willing to do anything to prove the strength of his love.  He asks Laertes, "Dost thou come here to whine, / To outface me with leaping in her grave? / Be buried quick with her?—and so will I" (5.1.256-258).  He asks if Laertes just came to her grave to whine and moan or to show Hamlet up by leaping into Ophelia's grave with her, and so he says that he will jump into her grave too, that he will even be buried alive with her in order to prove his love is greater than her brother's.