I have never raided, but heard most raids are 10 or 25 man raids. When you only raid with 10 players, are their less enemies then if you raided with 25?

Also, unlike a dungeon, you do not que for a raid you have to manually ride/fly there? Is there a website or a map with the locations of these raid instances? Thanks!

Raid groups have changed as new expansions were released. Current raiding options include either 10 or 25 man groups and the dungeons essentially scale in difficulty based on the size of the raid. The number of monsters/bosses doesn't change but the health and damage is reduced for 10 man raids. Additionally, the amount of "loot" is decreased for 10 man raids. For some fights, the mechanics may change slightly to allow for limited raid size composition. As an example, a fight in the WotLK Naxaramas instance required two priest (preferably shadow spec) to mind control units that would then tank the boss. Since a 10 man raiding party wouldn't likely have two shadow priest, the 10 man version provided crystals that any party member could use to handle the necessary mind controlling mechanic of the fight.

As for queuing differences for 5 man dungeons versus raids, you are correct that raids require you to travel to the instance entrance (or get summoned by other party members already there). With Cataclysm, changes to the queuing system for 5 man dungeons also requires that you at least visit the instance entrance once before being able to queue for it, but after the discovery, you can queue for it from anywhere in the game (as long as you meet level and item level requirements). To locate any of the instance/raid entrances, a useful site to check is wowwiki.com This wiki style site includes topics on the instances and the content (bosses, trash mobs, history, etc...). Another site, wowhead.com, provides gear, quest, and instance information as well. I tend to go with wowwiki for instance information but other sites have good information too.

the difference between 10 man raids and 25 man raid its not that there's more people its just that the um... monsters or whatever NPC's have more health and have higher attack and a good site with maps and anything else u need is wowhead.com hope this helped

so, ya, what you said is correct, they have either more enemies in 25man, or lots more health (bosses generally more health), some fights in wrath of the lich king were different in 10man version than in 25man version, but I'm not sure about cataclysm yet.

and yes, you do have to go to the location yourself for the raid, or a fellow raid member has to summon you.

http://www.wowhead.com/zones=3.3

that has the list of the different raids in cataclysm. When you go into the raid's site, there is something bolded that says "Having trouble finding it? Click "Location" in the Quick Facts box to the right!" when you do that, it will take you to a map that has a yellow dot on it where the entrance for the raid is at.