<a href="http://web.site.example.com/long/URL/goes/here"> http://web.site.example.com/long/URL/goes/here </a> (without the spaces, of course)
If the URL is long enough, the browser can't break it to wrap the lines, and so your readers wind up having to scroll right and left for all of the entries on their friends page.
Go ahead and put the link in as a link from some meaningful, and wrappable, text. Someone who wants to use the link somewhere else can always use the "copy link to clipboard" function of their browser.
Update: It appears that LJ automagically makes anything that looks like a URL into a hyperlink. Grrrrrr. That means that folks usually don't repeat themselves, as above, but simply put URLs into their text. Bleagh. Put them in as links, please.