I found 5 mods on Nexus that allow you to create more than one constant-effect enchantment on clothing and armour, and I was wondering what people would recommend if they have used them, or if there are others that people found good.

It's been a while since any of them were updated. I installed Multiple Enchantments (which I think should really be called 'Hammer of the Master Smith'). It's a small quest mod with a special enchanting chamber and objects. It includes a test mode, which I tried and found glitchy.

Here are the links:
http://www.tesnexus.com/downloads/file.php?id=18072
http://tesnexus.com/downloads/file.php?id=9423
http://www.tesnexus.com/downloads/file.php?id=24915
http://tesnexus.com/downloads/file.php?id=8862
http://www.tesnexus.com/downloads/file.php?id=11455

I personally use Enchantment Mastery, which has worked excellently for me, only having (what I think may be) a glitch when trying to place certain constant-on-self enchantments onto weapons. It's nothing big, they just don't seem to get applied to you sometimes.

Mage Craft is also good. What I used.
http://www.tesnexus.com/downloads/file.php?id=15587

I'll second Enchantment Mastery. I've used a couple others, and this one is the best I've run into so far.

Some enchantment mod can be used together, though I cannot ensure there won't be any conflct between them.

- If you want to make your own cheat item in-game, you can use 'Multiple Enchantment Effects on Apparel' with UI tweak like 'http://www.tesnexus.com/downloads/file.php?id=17284'.
It works like: When you enchant the token, you can enchant it as normal weapon(the token is actually weapon item), then the mod will move the enchantment to armor/clothing you choose(you should enchant the item first to give unique formID, though). However, since it modifies vanilla enchanting altar script, it may conflict with any other mod that changes enchanting altar script as well. Also, for some reason, you cannot use some of magic effects for multi-enchanting.

Put me down for another vote for Enchantment Mastery - Of the(several) that I've tried, it's the only one that appears to be bug-free(excepting the constant-effect-on-weapons thing that Bibliophile mentioned, although I've never attempted that type of enchant myself) - does what it claims, no muss, no fuss. Good Stuff. Also, if you use Supreme Magicka, you can use the SM .ini to tweak enchanting still further.

Enchantment Enhanced has a (significant) limitation that allows it to work properly only on pre-filled soul gems and not on soul gems that you fill yourself. In the comments the author states that he is aware of this but has no intention of updating so you might not want to use it. With everyone recommending Enchantment Mastery I just have to use it myself now - thanks!