Contrary to what dvdane wrote, my understanding was that a ronin did not lose his status as a samurai when he became a ronin, he was just a samurai that no longer served a lord.
It is true, that the ronin technically is a samurai no longer serving a daimyo. But it is not as simple as that.
Samurai is technically just a term describing someone who is paid to serve, but there was a caste within the samurai. Not all samurai where for instance allowed to carry shoto (long/short). Simply footsoldiers, spearmen and light spear cavalry were also samurai, but just low and recieved very little pay and respect. Some of them were not even allowed to wear armor. The general samurai, as we know him, was an officer and some had a status of nobility, especially if he held an admistrative post. Some samurai even had their own houses and as such their own insignia. Of the "real" samurai, the lowest is the ba-samurai, horseman, who was allowed to wear bodyarmor, facemask and wear shoto. Above him was four higher ranks, where the two highest were administrative positions at the shogunate.
For a samurai to belong to a house was important and of great honor. It usually meant that the house had been samurai for generations, and thus each house had its own style of combat. To be recognized for ones swordmanship was a huge honor. The greatest swordsmen were allowed to test the daimyos swords, to train his samurai and the best of them all, became keishakunin.
So for a samurai no longer to be employed by a daimyo meant loss of the rank he held, the status, his income, his house and so on. Unless the samurai had put away enough money to get himself a house and live decently, the samurai had to seek other employment, which in many cases meant to work beneath class, and those belonging to shinokosho considered those who did below them, which meant next to hinin and chori (outcasts).
Thus many ronin became bandits, yakuza, bodyguards, some became farmers or merchants, and some sought permission from a daimyo to perform seppuku.
In discussing the samurai, the ronin however is as interesting a character as the samurai, as the ronin is relieved of all social responsibilities and, most importantly, of giri, the duty. Giri is very important. To demonstrate it, let me tell a giri tale:
A samurai was attacked by four thieves and fled the scene. When his son discovered what had happend, he asked his father about what had happend, fearing his father was a coward. I did not flee because I was afraid my son, I fled because if I had entered combat, I may had injured myself or even died, and I had not permission to die.
Giri takes away any free will. A daimyo owns his samurai and can order him to do anything. If the daimyo wants his daughter as mistress, he will give her to him, if the daimyo orders the samurai to take his own life, the samurai will do so. That is giri.
Of course giri allowed for abuse, and in those cases the samurai could either go to the provicial lord and complain, or if of a certain rank, complain to a magistrate at the shogunate. Finally he could perform one of the 8 forms of seppuku, and commit suicide to protest against the actions of his master. If doing so, the provincial lord would investigate and the daimyo would thus be punished.
It is easy to see the burden of giri. A ronin was free of it and could act on free will. The best depiction of the freedom of a ronin is in
Shichinin no Samurai, where the old ronin shaves his head, removing his hairnot.
It is very wrong to consider ronin as freelance. That is not how the system worked. A ronin could not just walk up to another daimyo and seek employment. It was very rare that a daimyo hired a ronin. First of all, it was peacetime and a daimyo was not allowed to increase his military strenght, ie number of samurai, and in most cases couldn't affort to anyway. All daimyo, except those close to the Shogun, were under strict supervision and even something as ordinary as fixing the gate required permission. So no daimyo could or would just hire a ronin.
However some did, and the only way I know of is out of the sense of giri. Many ronin would ask a daimyo for temporary service, so that they could perform seppuku and die a samurai. Some daimyo were so impressed by these actions, that they employed them. Then again, many ronin used it as a trick to get employment. However such cases were very rare, as if you asked to perform seppuku, you were allowed to.
So there is one hell of a difference between the two. I hope I made it somewhat clearer.