3x Ukraine questions

1) Is 1 May celebrated in Ukraine at all - are shops and attractions open? If it is celebrated, what happens?

2) I would be really grateful for an explanation on how I can go about getting a Ukrainian prepaid Sim card for my mobile? What is a good place to by it, what documentation would I need to show, and what, roughly should it cost? Any idea whether international calls can be made from prepaid SIMs? (believe it or not, I have never used prepaid SIMs, I've always had a subscription, so I don't know about this in English either... ) This conversation is well over the level of my skills in Russian, so it's important that I know exactly what to ask for..

3) What maps can be used online for checking addresses in Ukraine? Google maps confuses things with bizarre transliterations etc, and it does not seem to be reliable outside the EU.

4) Is it not needed to use a credit card when BOOKING a hotel in Ukraine? I have never personally booked a hotel without using a credit card and I do not feel confident that my booking is valid, since I was not asked for it....? I booked online and ticked that I would use "money" (meaning, cash, I guess) to pay for the room, and just clicked submit. There was no field for entering credit card details.

3) http://maps.yandex.ru Type the city name "Одесса" in the search field. If the scale is big enough the streets are marked with both Russian and Ukrainian.

I am not a Ukrainian resident as you know but I can answer two questions.
1) Yes 1st May is celebrated and I guess many shops can be closed (exept groceries of cause). About celebrations I dunno, I guess it's some labor union marches in big cities like in Russia.
2) You can buy Ukrainian pre-paid sim card everywhere in Ukraine, it's pretty easy and cheap. You only need to show ID (I guess your passport would be enough). Little shops that sells mobile phones and sim cards are everywhere, you just can't miss them, especially in such a big city like Odessa. Also Ukraine had one of the cheapest prices for cell-phone calls in Europe, at least it's much cheaper than in Russia and our prices also quite affordable.

1) It differs from city to city. Banks and some stores will be closed (mostly because it's Sunday), attractions are usually open.
People don't celebrate May 1st as they used to do. Most think of it as of beginning of spring and a day off, when you can meet your friends and go on a picnic. Demonstrations are possible, but few people take part in them.
2) Basil77 is right. SIMs are cheap, usually 2-5 dollars, depending on rates and mobile provider. You can ask a sellperson for advice (what SIM you should buy depending on your goals - calls abroad, local calls, etc.), because conditions are very different. They also can help you to add money to your mobile account - for free or for a few grivnas. I've never was asked for any ID when I bought SIMs, but maybe something changed lately (I doubt, though).
3) CoffeeCup's link is great. If you need a paper copy, you can buy a booklet with detailed map of Odessa near the train station. Such maps usually have public transport routes. It's very useful. ;)

Does anyone know about MicroSD cards? I need one. Have never bought it before. What chain of shops in Ukraine might sell it? Again MegaMaks?

Wherever they sell cell phones they sell those too and it wouldn’t be too big of a stretch to say it’s on every corner. I don’t think Ukraine is any different from Russia in that respect.