Flicker and shutterfly and snapfish OH MY!
A quick Google search shows that there is a plug in for lightroom to export photos to picasaweb.
Picasa and picasaweb are actually separate utilities. One being the online storage and sharing site, the other being the free software loaded on the PC for editing and sorting.
If you already use lightroom, then like the other guy said, Picasa becomes redundant. But picasaweb is still a good site for sharing.
I haven't used any other site like flickr for my 5n pics tho. I've been a long time photobucket user and found it completely unsuitable for my 5n pics, but i still find it convenient for uploading camera phone pics and random, non photo images.-- hide signature --
Sony NEX-5n (noob)
If you have lots of photos, Picasaweb doesn't give you much compared to Flickr. There are also APIs far beyond what Google offers even now. If you're willing to spend about double for 500px ($50/year), this is the one service which seems to present photos in the best way possible, since this account level offers personalized portfolios withouth the hassle of wordpress. You can also dabble in the sale of your photos without having Flickr yell at you.